Way back before your time girls wore micro miniskirts. I was in the checkout line at my military post exchange in Vietnam and the girl in front of me was leaning over her shopping cart so her skirt was pulled up over her panties and she got pissed when she noticed me looking. I was 18 and that's what we did.
those girls are looking for attention. its just they are trying to attract certain men and when the men they dont want start trying to get her attention then she gets upset. i think a lot of girls are that way now a days. especially online where people can post certain pics of themself or say sexual things to draw men. but they mostly will draw the creepo types with type of lifestyle and how they are coming across.
its saying 'I want you to notice me' though. And if a guy notices you he could hit on you and we know that. We choose what we wear and we know what kinda reactions we'll get if we had our boobs out vs if we didn't. So it might not be saying hey come hit on me but its wanting that sort of attention- to feel attractive
@Itsprincess: If I'm wearing a short dress it usually means more like "It's 98 degrees out and I don't wanna wear a long dress." But then again I don't hang around bars and clubs to look for attention like many others do.