Men cheat for the same reason that dogs lick their balls... because they can.
Do not be too moral. You may cheat yourself out of much life so. Aim above morality. Be not simply good; be good for something.
Henry David Thoreau
If you have to lie, cheat, steal, obstruct and bully to get your point across, it must not be a point capable of surviving on its own merits.
We are more likely to cheat if we see others doing so. We tend to conform to accepted norms of reasonable behaviour, rather than adhere to strict rules.
Eighty percent of married men cheat in America. The rest cheat in Europe.