most normal men like girly girls because most girly girls like normal manly men, that's why. it's a kind of balance. they like girls to have everything they do not and cannot have. and that's how nature want us to be. girls who are not girly don't satisfy men mentally as men who aren't manly don't satisfy girls. so the more girly you are the more their minds get attracted, that's all. though i don't think "all" men like so much girly girls. there is a kind who like more mentally active clever girls because they themselves are more active and more clever than other men. but these kind are rare.
because if we were looking to date someone who looked like a boy, we'd be gay! Seriously, not all men like 'girlie' girls - they actually annoy me... but equally women who flaunt their femininity we're naturally programmed to adore.
I don't think you refer to girly-girls as much as women who simply dress up. Well, a lot of people are just attracted to that instinctively. But if you ARE referring to very feminine women, that's because a lot of men want women who make them feel more manly.
Which...is not my thing, but it's a harmless fantasy. And there are women willing to cater. So yeah, whatever floats your boat, guys. :P
A lot of the times, its because guys think that they're confident. And which guy doesn't like a confident girl? But if its a really vain or shallow guy, then he's only after their looks. But think about it this way, what happens (most cases) when a guy finds out who that girl really is behind all that make up, clothes and jewelry? It doesn't always work out. A lot of girls think that make up makes them beautiful but its true that if you're not beautiful on the inside, eventually it will show on the outside, your personality is what attracts a guy. Well, most guys that is. If a guy is only after a pretty girl, he's not the type of guy you want to even be with, that says a lot about the type of guy he is and how he'll treat you.