Adding screencaps not optional?

Honestly, I don't know when it happened. It's just been like that for a long while, now. As for why, I can't tell ya' that either, fanpop has a bad habit of doing things without telling anyone, I'm afraid.
They really love leaving people in the dark, don't they? 😒

The screencap section in Images was removed a few years ago. However, I don't think that means you can't add screencaps at all - you can put then in the Photos section instead.