Just today someone started a discussion about the videogame Resident Evil 0, which led me to wonder if there are actually any prequel stories that really added something to a series in a way that improved it.
And we soon came to the conclusion, that usually these stories only attempt to answer questions we either never wanted to know, or provide banal explanations for things that seemed much more fascinating when then were left obscured.
One of the big reason prequel movies and videogames exist is because it allows the creators to get more money out of a well known brand even after the story has been wrapped up, all the villains killed, and all the problems solved. If you can't continue a story, then adding additional chapters in front of it can still be done.
But generally the stories aren't improved in any way or tell us anything really new. And after all, you already know how everything will turn out. For action movies that are all about spectacle that's not a terribly bad drawback because often the story was already pretty thin to begin with. But books can't really rely on cool action scenes to sell the story to readers. There needs to be some meaty plot or character development to get people to read it.
Which is probably the reason why we see it so rarely attempted with books.
