Why didn't Obi Wan or Uncle Owen change Luke's last name to protect his identity better?

Few people survived who knew that Anakin had turned to evil, and even fewer knew that Anakin had survived (just Obi Wan, various evil people, and, in his omniscience, Yoda). Certainly no one on Tatooine nor any of Luke's relatives knew his father was alive. Anakin disappears during the Clone Wars, much time passes, and a new Dark Lord of the Sith appears. What's to connect them?

Looking at it another way, Obi Wan took Luke to be raised by his only living relatives (since he clearly had no aptitude for parenting). Owen couldn't have raised Luke with a different name and still claimed to be his uncle. Further, Owen might have hoped that Luke would redeem the Skywalker name from the rambunctiousness of his brother, and since he and Beru had no kids of their own, they wanted to raise Luke as their own. Any child they took in would have become a Skywalker.

So, yes, it may have been wiser to drop Luke off with strangers, but for some reason Obi Wan didn't do that. Given that he didn't, changing names wasn't an option.

I can not answer this question without asking another, When Shmi Skywalker married Lars and conceived Anakin's half brother,(who went on to raise Luke Skywalker) why was the family name "Skywalker" to begin with?

First, the thing that must be understood here is that Anakin thought that the child (he didn't know she was carrying twins) had died with Padme. With that in mind, it is safe to assume that the emperor thought so as well, until Luke showed up on the radar. No one was out looking for Luke, or Leia, until they grew up and joined the Rebellion.

now, having said that, another thing that should cross our minds is that Bail and his wife formally adopted Leia. While she may have known that she was adopted from whatever age, (See Episode VI, the scene in the Ewok village just before Luke leaves to face Vader), she had already taken on her adoptive parents names. That, and in Episode III, I don't recall it being said outright that Padme had taken Anakin's name...and when the Organa's told Leia that she was adopted, they would have only mentioned that she was the daughter of Padme Amidala, no need to mention that Anakin was the father (and in my opinion, Bail didn't know who Leia's biological father was).

Now, with that out of the way, we can focus on Luke, and the fact that he was raised by his Aunt and Uncle...on Tattooine...which is in the Outer Rim (Episode IV, Luke telling C-3PO where he is). In Episode II, Anakin, by way of his actions and his tone of voice (I can't quite remember if he says it outright or not) makes it apparent that he has no intentions of coming back to Tattooine, because there is nothing there for him. Also, in Episode II, the only people that Anakin and Padme have interactions with are Watto, Owen, Beru, Anakin's step-father, and the village of sand-people that Anakin annihilates. Now, by taking Watto out of the picture (A, because he lives in a completely different city than where Luke is around, and B: we simply don't know the life-span of troydarians.), the only people around Luke who could have guessed who his father was are Owen and Beru.

Also, we can probably safely assume that Obi-Wan had told Owen, at some point in his exile, about Anakin's fall to the Dark Side, and had also warned him to keep Luke safe. I presume this because of how angry/defensive Owen gets when Luke asks about his father. I can only imagine what was going through Owen's mind when he heard Luke talking about going to the Imperial Academy. Luke was safe on Tattooine because it was out fo the way, and no one knew who Anakin (or Luke for that matter) was, but the Emperor would know.
And that is why, when Luke finally joins the rebellion and his name is practically announced to the Empire, the Emperor (being a shrewd man -- he had to be, he hid from the Jedi for so long) puts 2 & 2 together.

I know this was rather long, but I had to tell you the whole of the story, or at least my understanding of it. It makes sense to me that, Owen and Beru thought that it would be okay to let Luke keep his father's name, simply because they were nobodies in the middle of nowhere.

Anakin knew that Lars was the last name of Cliegg and Owen. It would not do well to hide him on Tatooine and give him the last name "Lars." Since Anakin believed the child of Anakin and Padme dead he would not sense to look for another Skywalker. Remember his mother died and Anakin had no father. But, to find a new "Lars" living on Tatooine could be a threat, especially if Vader was looking for the Lars family to destroy all memories of his painful past or merely to eliminate any who might know his true identity. After all, Owen and Beru were murdered. For missing droids, yes, but remember what message the droid had. So why not change Luke's name to something else entirely... isn't it true that Anakin should have been the greatest Jedi ever only he was too old when they first found him? Keeping his last name Skywalker as opposed to anything else, would help Obi Wan to keep track of him and when he was ready, and when Owen was not in the way, he could allow Luke to know his true identity, as a constant reminder that there is good and evil in all of us and to always remember what can happen to even the best of Jedi when they allow themselves to be vulnerable to fear, anger, and hatred and go to the Dark Side. Obi and Yoda want Luke to know that to hate Vader is to hate himself. Overcoming this is where Luke surpasses Anakin and becomes the chosen one.

On a side note, it is also important to remember that Owen was Anakin's STEP brother, NOT his HALF brother. Owen's mother was Aika from Ator. So the children of Beru and Owen would have the last name Lars, not Skywalker. Schmi most likely kept the name Skywalker for herself in hopes that it would make it easier for her son to come back and find her one day. Also, for the most part, many women in this Galaxy kept their maiden names. (ie: Beru Whitesun)

There are several answers to this but the one that
is the best is this Anakin hated his home planet.Even as Vader he would not go back there.

lukes last name would not have been skywalker if owen had changed it because owens last name was lars NOT skywalker so they really wouldnt have cared at all about the skywalker name because it wasnt theres i realy dont know why they would keep the name skywalker other than to help out the viewer its good for that and thats all

i dont know but i think that his last name is better like that...................skywalker.....................hmmmmmmmmmm

Vader hated Tatooine, and that is where Obi-Wan went into exile and Luke grew up. Tatooine is not part of the Galactic Republic. Once you are a Sith you no longer obey your Jedi name or human name. Like Vader said " That name no longer means anything to me" Luke was only discovered after he destroyed the Death Star with a single shot, Vader and the Emperer figured he must be strong with the force to do that. If he stayed on Tatooine he probably would have never been discovered. IDK this is a hard question but it was the best I had.

Hm... Good question, this is. I believe it is because, well, Darth Vader wouldn't be looking for him because he thought he died with Padme. And, he's on Tatooine. Darth Vader HATED Tatooine. Why look fo him there when he doesn't even think he exists? Plus, the household he lived in was called Lars, not Skywalker, so it wasn't really that suspicious. I don't know, maybe Lucas just thought, 'meh, I like the name Skywalker.' Other that that... I got nothing. The universe may never know the real reason...

Well they hid Luke from Darth Vader on Tatooine so their was no point because no one knows that Anikan Skywalker is Darth Vader

They had no choice but to name him Skywalker. For example, assume Cliegg Lars was still alive when Kenobi appears with the baby Luke. The next day, the conversation goes like this...

Random Citizen of Tatooine: Hey Cliegg, who's that baby? Slave baby? Who did you buy him from? Hey, you didn't steal a slave baby, did you?

Cliegg: No, no. Remember my deceased wife, Shime? Her boy Anakin was freed like 15 years ago?

Citizen: Of course! I saw him all the time at Watto's junk yard until he became a famous pod racer. Only human to ever win a race. And about the only person I ever knew that got off this sunburnt rock. What ever happened to him?

Cliegg: Oh, he died. Yeah, died in an accident on an umm, freighter.

Citizen: Unbelievable!

Cliegg: Yeah, you know the um, spice business around Kessel is pretty, ah, risky and... Well anyway, this is Anakin's son, Luke. I'm the only family he has left now.

Citizen: Well, nice to meet you little, Luke Skywalker. Say, you look just like your daddy did. Look at those eyes.

Cliegg: Yeah. Well, I might die any day now, so Owen will have to take care of him from here on out.

The simplest answer is probably the right one, and love is the most powerful Force in the galaxy...
Owen and Beru did not keep Luke's name the same as his Father's, rather, they kept his name the same as Anakin's Mother, Shmi, in HER honor. She and Cliegg Lars were very much in love until she was stolen away, tortured and eventually killed by Sand People. It was likely Cliegg Lars' request or demand or Owen's way to honor his father's last dying wish- A memorial to Shmi and his father's marriage. This was probably done despite Obi Wan's great and numerous objections, as it really would be safer, less obvious, to say Anakin was the LAST Skywalker. But Cliegg was a stubborn old cuss, and loved Shmi so very much, and Owen really didn't trust or like Obi Wan(or the Jedi in general) and so continue with Luke, the Skywalker name would.

I haven't read all these answers so I don't know if this has been posted yet but the answer is simple. There is no reason to believe he didn't go by Luke Lars! The name Skywalker is NEVER mentioned until Luke rescues the princess on the Death Star! He could have gone by Lars his entire life until after Owen and Beru died and Obi-Wan told him tales of he and Anakin (still a name not mentioned until later in the saga) fighting together in the Clone Wars, etc. This could have happened on the Falcon during the journey through hyperspace on the way to Alderaan. This could have prompted Luke to decide to go by his father's sir name, Skywalker. Then, when he rescues Liea, that is the first time he ever says to someone: "I'm Luke Skywalker...".

Because Skywalker sounds cool.
Luke Lars sounds like more like an IT guy than Jedi.

I assumed it was because Obi-Wan was living nearby. There's a tension between the Lars and Obi-Wan. They couldn't pass him off as their son because "Old Ben" could tell him the truth at any time, he could take him away at any time (no adoption laws I'm assuming) so they opted for foster parent status.

I always feel a bit bad for them because of that.