Why do men cheat?
I am a lover of all creatures, but I especially love ducks. In my experience, ducks are inquisitive, comical, and deeply intuitive. For many years, I lived near a mallard who would occasionally join me for tea, scones, and interesting conversation. One day, I remarked to the mallard that I was having difficulty hearing him speak during our interesting conversation because a nearby horse was whinnying. I'll never forget the way he looked into my eyes and said, "You have jam on your face." Then, he continued eating his scone.
I'm telling you about my conversation not because I think you should have lunch with the mallard. (He's very busy, and likely doesn't have time for you.) I'm telling you about him because this moment with the mallard made me realize that time spent scrutinizing other people is, in most cases, better spent scrutinizing ourselves.
Your preoccupation with why men cheat has kept you from asking the bigger, better question: why do you choose to cheat or choose not to cheat? This is the question whether you are a man or a woman. Why is faithfulness important to you, or not important at all? You can't know the reason's for another person's behavior, and I couldn't stop the horse from whinnying. But I could wipe the jam from my face, and you can attend to any that may be on yours.
Attend to yourself. This is the only choice.