why men cheat/

Many reasons.
the most common one is because they are bored.
also modern culture treats men like idiots these days, so there is no standard of behavior for men to emmulate.
Also, In some cases, women use love as a weapon. A friend of mine had love exactly twice a year, and his wife treated it like a chore.
Men are starting to realize they don't need to pander to spoiled princesses, and are doing what they want to.
I'm not saying it's right, I'm saying our culture, and it's gender roles, encourages it.