Do you think most people cheat and feel guilty?

I know this girl who is close friends with my cousin. She’s been married for 5 years and my cousin found out that she has a boyfriend that her husband doesn’t know about. My cousin asked why she cheats and if anything was wrong with her marriage. The lady said that nothing is wrong with their marriage, it’s like perfect, they’re very happy together and that she loves him. But she feels like she wants more…in a way of being greedy. Having a “bad” boy…so she cheats on him and doesn’t feel bad about it. Her husband trusts her completely and has no clue.

I’ve met a couple people who cheat just because they want more. Do you think most people are like this? Cheat because they just want more and it has nothing to do with their relationship? Makes me feel bad because her hubby trusts her and has no idea.