ahh...to be a helpless little girl
in need of aid...the kind of aid most likely to be in the form of some big strong male
type...and when he comes to rescue you from, say, locking yourself out
of your apartement, or a broken-down car on the side of the road...your gratitude is overwhelming, and you feel the need to express it in, well, physically affectionate ways...especially if he's cute
it's simple, really. after being saved from who-knows-what, a wussy little girl will say to herself, 'self, how can we repay this guy for being generally courteous and saving my ass? what do boys like? sex, of course. let's throw ourselves at him, shall we?' and sleazy behaviour ensues.
and guys realise this, unconsciously, at least. which is why they always stop to help pretty girls, even to the point where a girl may not even need help. she may be fine on her own, but the knight in shining machismo will jump in her way to save the day.