Some men seem to crave sexual excitement and one woman is not enough for them. Even when his wife is loving and faithful, it is as if he has a gaping hole of sexual need which is never filled. A man such as this needs a lot of help and intervention from a professional counselor and a support team which can walk with him through the changes he will need to make in order to find true love. But this is only possible if he himself is willing to acknowledge that he needs help, and is willing to radically change his attitudes and lifestyle.
People don’t usually want to have affairs, even men who cheat a lot, but they are compelled to do so because it gives them something they can’t get anywhere else. Whether that’s a sense of self worth and desirability, a more dangerous/daring sex life, or the ego boost men experience by being with someone younger, there’s always a need that drives sexual misdeeds, although the cheater may not know what that is. Usually the need arises from some fear or insecurity, and men in particular are disallowed from showing those feelings, so the fear gets mangled and transformed into a bad behavior instead.
I think the reasons men stray outside of the marriage are varied. If it is a very young couple perhaps they married too soon and he feels that he never had a chance to really experience much of the world before he was led to settle down and be a husband. If the couple has been together for many years it could be that the relationship has been deteriorating for some time and an unfortunate (or fortunate) opportunity presented itself which made it possible for him to cheat. It could be that one of the partners suffers from an illness that prevents that sort of physical connection that all humans need and so he went looking for it somewhere else.
Men sometimes need more attention from their wives and she’s too busy taking care of the children and the home and doesn’t make time for him. When he comes home from work there is no hot meal or a nice word, just complaints about what happened in the house with the kids or at school or her mother in law.