Because women think with their vaginas -- that is, they use their awesome sexual power to control, manipulate, and get what they want from men. And men let them get away with it.
I don't know if women think with their vaginas but they do know a man's sexual appetite is usually a trillion times hers, so by default she probably has to think with her vagina to have some sort of control. A woman hates a "player" because she has no sexual power over him and cannot manipulate him, yet still finds herself attracted to him. HE has the awesome sexual power and her vagina has no value.