Metadata. The same way you might group music files per artist or per album or per genre or in playlists but the filesystem only allows for 1 type of grouping without duplicating the files or some weird shortcut kind of thing. You can group per author or per genre of ebooks or whatever. Granted it's less useful compared to music but it does make sense and I prefer media to be displayed as a library myself.
Exactly. I am a big fan of Calibre for books, iTunes for music (granted, iTunes is mediocre monolithic software), and generally software (adapted to the specific media type) that manages the library and metadata, so I don't have to touch the filesystem.
How are you going to play music you've added in the last three years, but not heard for a month, from the "Latin" genre, with two or more stars, using only the file system? With an iTunes smart playlist, it's trivial.
In Calibre it's trivial to sort the books by Title, Author, or (my self-defined and filled) Genre column.
How would you even start to manage photos in the file system? By name?
> In Calibre it's trivial to sort the books by Title, Author, or (my self-defined and filled) Genre column.
honest question: why would you ever like to do that?
I find calibre unusable because of these things. I just have one epub file and I want to read it. However, the damn program forces me to "initialize my library" and other bullshit.
>How would you even start to manage photos in the file system? By name?
Photos is actually an exception for me due to the personal nature of them. I group them in directories based on date ranges and events. I don't want to upload them to some webapp or cloud storage for privacy reasons.
> How are you going to play music you've added in the last three years, but not heard for a month, from the "Latin" genre, with two or more stars, using only the file system?
BeOS actually solved this 20 years ago with its file system BFS. Haiku is an open source reimplementation of BeOS that recently progressed from (high quality) alpha releases to its first beta.
