Thread:Jekkers/@comment-4311395-20140916015622/@comment-25035274-20141006113707

I can't speak for every case, but in some cases the Fan Fiction category isn't added to a page because, as Kuruni pointed out, the page is already part of a sub-category of Fan Fiction. By doing it that way, it allows the page to be reached by drilling down, and reduces the over-all clutter on the Fan Fiction category page.