It’s one of the like “stock” plot devices. It’s one of the only ways to get people to do something out of the ordinary, like deciding to go on a killing rampage, or to blow up nazi’s or whatever. Not to mention the concept of seeking revenge is something that I think a lot of audiences enjoy seeing because it’s something they themselves cannot do. I know we all have our little grudges and betrayls and whatnot so they idea of settling the score is fascinating.
