It could be that he really likes those stories and thinks you might not have fully grasped them the first time. So he tells them again. He might also be forgetful and not realize he has already told you those stories.
Maybe she just has a limited repertoire of stories. Or perhaps those are her favorite stories and she wants to share them over and over again because they hold special meaning for her.
Maybe he just doesn't have much experience in storytelling. He might not have read enough good stories to learn from or practiced enough to develop his own style.
Maybe they just really love those stories and think they're worth sharing multiple times.
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.
It could be that those stories have a special meaning or lesson for them and they want to emphasize it. Or perhaps they have trouble coming up with new ones.
Maybe she trusts you and wants to share her life with you.
It could be that he doesn't know his audience well. He might think that the things he finds interesting are universal, but in fact, they are not. For instance, if he is really into some very niche hobbies and only talks about those, it can be boring for others. Also, his storytelling skills might be lacking. Even if he has great stories, if he doesn't know how to present them in an engaging way, like lacking proper pacing or not using vivid language, the stories will come out boring.
He could be trying to teach you a lesson through that story. He thinks it's important and wants to make sure you really understand it, so he keeps repeating it to drive the point home. It's his way of making sure the message gets through to you.
Sometimes people tell the same stories over and over because it gives them a sense of comfort or connection. Maybe they have trouble coming up with new things to talk about, or they feel that these particular stories define them in some way.
Maybe they just really love those stories and find them memorable. Or it could be that they think others haven't heard them before.