Why do people cheat?

Please note that this question is not the same as Why do people cheat on their partners.

People normally lie and cheat because the are basically lazy or inept.

The behavior if not controlled when they are young ends up manifesting itself in their adult life. The more successful they are are cheating and lying the more the feel that this the correct way to do things.

They are not satisfied with their current relationship or have very little self-control.