Comment by the_af

There's nothing left for your imagination to fill in if there's official content (or expanded universe stuff) making it explicit for you.

As an example, nothing George Lucas did compares to what I wondered about the mysterious clone wars back when I watched (and rewatched) Star Wars. Lucas effectively "filled in the gaps", leaving nothing to my imagination. That what he did envision turned out to be pedestrian only added insult to injury, but now I cannot unwatch his prequels.

There's a similar phenomenon to when you read a book and imagine the characters and even situations mentioned off hand in the text, and then someone makes a movie out of it and makes it explicit and locks in specific actors and CGI-filled situations for whatever you imagined in your mind. You may or may not like it, but your own imagination gets stifled.

For things like "The Hunt of Gollum" it becomes downright bizarre. Whatever became of Gollum as he crawled towards Mordor, tracked by Aragorn and later mentioned by Gandalf, is such a minor footnote; definitely something for your imagination. Tolkien definitely didn't think it warranted even a short story. But no, they must make a movie out of it, because why not; the fans will lap it up even if it garners bad reviews.

As I mentioned in another comment, and there's no polite way of saying this, the nerdy need to know "what really happened" in excruciating detail (not to speculate, but to know) is a sign of immaturity. Art, even pop art, thrives as much in the known as in the unknown. To want to cast light into every single detail and "make it official" is a mistake. Though of course publishers and studios salivate at the chance of milking the proverbial cash cow.