Why do some married men want to be with another female when they are still married?

This man who lives near me I thought was single this whole time he asked me out a while ago. Then recently found his profile that says he is married since 2014. Then his wife shows up to town to be with him when she was not with him this whole time he lived here. Why can't couples stay together or not get married at all? So that affairs to not start or rupture.

Why do some married men want to be with another female when they are still married?
Post Opinion