was once a SS shipper when I was a little girl, yes kill me now, so:
-Sasuke and Sakura look good together in terms of appearance.
-Initially if you were the typical hardcore Sakura fan, you would want to support her and since she loved loves Sasuke... yeah. (Oh and also you would hate Karin).
-Sasuke is a handsome man = fangirl fantasies. If Naruto was a shoujo, and Sakura is the protagonist, Naruto and Sasuke as her love interests, fangirls would immediately root for Sasuke cause he's the bad guy with the cold attitude. It's all shoujo cliches. Even now, the cliche is still alive. You know bad guy always gets the girl *shivers*, typical shoujo. And of course every series has fangirls.
P.S. Nope, not a fangirl, never hated Karin, but had my shoujo fantasies, a long long long long long time ago. Besides putting myself into a SS shipper's shoes, there's no way I could appreciate the ending. I mean what kind of author tells you that he has no idea how they ended up together and still paired them together. What's the point?