A cheater is solely responsible for the infidelity. “Why do people cheat” is less important than the cheater acknowledging it was their choice. but each person is tempted when they are dragged away by their own evil desire and enticed. Cheating is a sin that one person does.

Who is to blame for cheating?

The cheater bears the responsibility for cheating

Generally, cheaters get the blame for their philandering because, it'd be illogical for the person aggrieved to also have to bear the responsibility for someone else's actions and indiscretions.

Why do people blame you for cheating?

Quite often the men say it's because their partner has lost interest in them, sexually. Women most often blame a lack of emotional intimacy for why they suddenly became erotically entangled with another man. "He understands me and listens to me in a way that my husband (or boyfriend) doesn't," is the common refrain.