Like with any published expanded universe stuff, reading about stories in between or beyond what’s portrayed in the official media is what I like about fanfiction - be it exploring the established world building and universe more or specific interactions and/or stories between characters.

i didn’t like the ending of a book series i read way back in middle school and i went online to search for “(book series) better ending” never found a really good one for that series but i’m glad it got me into fanfic

A desire to do better by a couple of side characters who I felt got mistreated by their series. Admittedly, I don’t read fanfics at all but I write two.

When I was waiting for books in a series to release (typically there’s a 1-2 year wait) I began reading fanfiction, especially if the book ended on a cliffhanger.

my love of Harry Potter + Kingdom Hearts!! Back in the golden days of the early 2000s