Sometimes I wonder if you post deliberately to polarize.
What if the real problem is not him or her or them? What if the real problem is you?
While I think it is commendable that you encourage women to look at their own behavior, this does strike me as a bit simplistic.
Most guys I know, the guys they know, and myself included, always keep an eye out for the attractive women passing by. And many of us would make a move, even if everything is otherwise ok in a relationship.
Personally I do not, because I am a man of my word, but the temptation is there, day after day.
I believe this to be a normal expression of male sexuality (so maligned these days) and perfectly healthy behavior for a man with a sex drive.
It does not mean one has to go through with it - and more to the point here, it does not mean our partner is lacking in something - it is just how we are wired.
Yeah, the desire for variety will always be there. Men and women alike. I think having children effects womens stability that way more than a lot of men. Just an assumption of course.
Sometimes people end up having mismatched sex drives, or one is more kinkier than the other. If they cant work it out, or one or the other refuses to even try, than people may seek out someone who does to be their long-term affair partner.
Third reason is feeling taken for granted, knowing one is unappreciated by their partner...then comes along someone who does.
Case by case, who knows if cheating is a "two-way street" or not.
I definitely believe there are people who can be monogamous til they die, why not?