Most Helpful Guy
The more scantly clad girls are seen as easier catches because they see to be giving it away for free. So the thought is "Why trouble with the other one who looks like more work when I could just get this one that is letting it all hang out right now?".
For a girlfriend, (insecure) guys want an untouched girlfriend. But just for flings or taking a stab at getting sex, they have no problem going for that easy looking girl.