Thoughts about "Roar"

So why is it that male characters in plays are always unfaithful to their wives? Why is this an accepted norm? Troy Maxson in Fences, by August Wilson, fathers a child outside of his marriage, married men in Tanglao-Aguas' When the Purple Settles run around with their servants, and Ahmed runs off with his wife's sister in Roar. Obviously, not every male character in every play has an affair, but I wonder if it's a coincidence that all the plays we've studied have this quality in common. It's kind of disheartening. Are these playwrights trying to send the message to the audience that infidelity is inevitable and that men can't be trusted? Interestingly enough, only one of these three playwrights is a woman. Does this mean that these male writers are disappointed in the way real men treat their wives? Are they endorsing this behavior? I don't know. I do know it doesn't make me want to rush into marriage.