Why do people cheat on their partners?

Thanks for the response. Yeah, I think that leaving under impossible circumstances would be a far better option. However, if kids are involved, the partners may mutually decide to work on their marriage for their sake. For example, scientific reserch shows that cheating is biologically ingrained in the minds but humans have adopted ways to control this tendency and accept a monogamous relationship. Some may feel let down by their spouse, unappreciated or even abused.