A man cheat when he doesn't have what he wants/likes. And sometimes what he wants/likes is too pervert to let everybody know, or, it cause a serious discussion with his parter. A man that is cheating, will be for that woman a very good man; he will say yes to almost everything, but he will get all he wants outside the house.
When he is not cheating, is when the house is a living hell full of fights every day.