There of course are men who wouldn't cheat! Good looking, successful and likeable men, as well as lesser 'catches'. I know lots of them. They just aren't wired that way. It isn't always just about being moral though; it's often about having a brain. Normal, sensible people get tempted too, but many think ahead to the likely consequences and think again. Especially if they are married to self respecting, strong women who they know would eject them immediately.
But among cheaters, I do agree that lack of opportunity is sometimes repackaged as morality or reformation.
I have a friend whose husband used to hold a very senior position in a hugely famous firm. She met him there when he was married and became the OW. His wife was on one continent (they had three kids) and he on another, with lots of access to young trainees and attractive women, far from home. He thrived on attention and excitement.
My friend became permanent and later married him and, because of their work, they were often living in different countries again. He had a number of affairs, most of which she discovered, but she suspected more. They split and got back together. Two years ago he got fired and since then has not really worked. He certainly doesn't have the access he used to to young women and his status has gone. This coincided with the birth of twins and a move to a house in a relatively remote area.
My friend still works in another country to him but feels like he would not cheat now because of the twins. I think she is right about the not cheating, but more because the opportunity is completely gone and he is now an unemployed man in his 50s! The closest thing he gets to young women is the one who works in the local supermarket. It's a good thing ultimately for her (she loves him and he provides stability) but it's circumstantial, I fear.