I don't get why all guys need to wear for a party is a plaid shirt, but girls have to stylize their hair, pick the perfect dress (that looks slimming to boot) or gown or not even a dress at all, apply make up and wear high heels.
Honestly, I don't want to do all that.
Because of the way other females in a girls' life taught her. Not sure how it started, though, but that's why I think that's the case.
But some girls feel most attractive like that regardless, and most people dress not to impress others, but to flatter themselves. That's what styles are all about.