There are plenty of reasons for people to cheat even if they don't actually cheat. If a spouse is not interested in sex or affection and just wants to live as roommates it gives their mate a reason to cheat. In many marriages one or both spouses are content to fulfill their roles as mother and father and pursue career goals but don't want to work on their relationship. Stuff happens as a marriage progresses. Just walking away from a marriage is not always the best option. I really don't blame some people for succumbing to temptation in situations. You cannot expect a spouse to just give up sex because you are no longer interested.