There are no reasons for anyone to cheat. Period.
Lack of morals, love, respect, or value for their partner.
Because he is a dishonorable douchebag, unable to keep his dick in his pants, and too cowardly to tell his currant spouse he is done with her.
That is really the only reason a man cheats.
Anyone who cheats [man or woman] sucks at life.
Because he is an idiot, just like a woman who cheats is an idiot.