Why do you think is Seohyun has less popularity compared to Yoona, Taeyeon, Tiffany and Jessica?

In the group, she is one of the 4 lead vocals, she is one of the 4 lead dancers, she is indeed beautiful and has a great personality.. is it because for example yoona is prettier than seohyun that people like yoona more? or taeyeon simply because she is the leader and as the main vocal, she has great voice. or because she is usually quiet and shy and very upright that people find her boring? well, i really want to know your opinion, not as a Seomate but as a SONE.. Thank you