If Kournikova were ugly, would she have won a tournament by now?
My guess is yes. If she looked like Mauresmo (sorry Amelie...), she would have been practicing hard at a stage in her career when she really needed to. Instead she was practicing, but also attending awards shows, modeling, music videos etc. If none of those distractions were there based on her looks, she would have nothing but tennis, and would have full motivation to improve. Furthermore, nobody would really care about or talk about "the streak," so there would not be unnecessary pressure added.
What do you all think?