It could be that they have a limited number of experiences to draw from or they have a strong emotional connection to those particular stories. Also, sometimes people repeat stories because they think others haven't really listened or understood the first time.
Some authors might get stuck in a particular style or theme, resulting in similar novels. But it's hard to point to a specific one without more context.
Narcissists repeat stories over and over because it helps them get the attention and validation they crave. Also, it might be a way for them to control the conversation and make it all about them.
Well, sometimes it's because the stories bring comfort or familiarity. Also, they might be easy to remember and share. And for some, they just have a deep emotional connection to those particular tales.