Is there a reason why so many romance stories and movies are always about cheating?

They always start with one person they end up throwing away for someone else they meet during the story, I'm sure you can think of a movie or show or whatnot just by reading this but they always make a move before breaking up with the person then the person that got cheated on finds out and their anger is part of the story 💀
Is there a reason why so many romance stories and movies are always about cheating?
Post Opinion