I assume this action is the result of immaturity combined with jerk personality.
Why do some guys do this? They'll date two girls and try to get sex from one and treat the other like a princess
It's all a game. A game you can put a stop to by keeping your legs and mouth closed..
There is an old mentality where there are the girls you bring home to meet mother and then there are the ones you party with. The ones they party with will never meet mom or get a ring or commitment. BTW the guys that do that are also the ones most likely to cheat in a marriage too.
Gator hit it on the nail!
Plus this type of guy will more then likely be the type that would keep one dangling around just in case a different relationship doesn't "work out." She is his "safe go to" girl so he is never without a female.