Queens! Men know almost immediately once they have met "the one;" the person that they will move mountains for. If he's waffling about committment, marriage, etc., you're a placeholder until someone they deem better comes along. In the meantime of course they want consistent sex, someone to fill the void, to quell their feelings of loneliness.

Men know immediately because that is how they are wired. Women, by nature, are more cautious, skeptical, and should be reticent in the dating stage. Women have more at stake, much more to lose. Thus we vet.