I think there's something to the old saying that women use sex to get love, and men use love to get sex. And love is really just a word we use to describe a close bond, or relationship, between two people. Men have been programmed to want sex, so they do whatever is necessary to be in a relationship with a woman. And a woman is programmed to want the stability and (financial) security of a relationship, so she offers the man what he wants: sex.