Monogamy is just the same. When two divorced people marry, four people get into bed. Ask your father. Bachelors have consciences, married men have wives. When a man steals your wife, there is no better revenge than to let him keep her.
Bachelors know more about women than married men do.
If they didn't, they'd be married too. There are a number of mechanical devices which increase sexual arousal, particularly in women. Chief among these is the Mercedes-Benz 380SL convertible. I'll come up and make love to you at five o'clock. If I'm late, start without me.