You seem to imply that it is simply the desire to have sex with other women that drives a man into the arms of another woman, and if that desire is sated in a safe in a legitimate way then the threat of cheating is neutralized.

But really... there are a LOT of other reasons--emotional and otherwise--why men cheat.

Your seeming need to micromanage the "outside" sex sounds like enough reason to make a man want to go rogue.