That’s because you don’t have media that doesn’t fit the artist-album paradigm. Not all music collections fit into that paradigm.
Some folks just use folders as playlists. They have a folder of “summer hits 2008” and want to play it that way. What Roon would do with properly tagged tracks in a folder structure like this would be to strip it down and put every track in as an incomplete album. That’s no good.
What Roon shouldn’t be doing is insisting on a major restructuring of how people have organized their music in order to use it. Sure, where a tool like DB Poweramp can add metadata that can be a partial resolution, but it does not resolve the case I describe above.
Then, as above, you have DJ sets, other things that don’t easily fit “artist-album.”
Finally, what if someone just brings a song over on a USB key or emails it to me and I just want to listen to it once through Roon’s RAAT transport without adding it to the library? So just stick in the key, navigate to the folder and play it once. These are simple acts that work with any media player but Roon. And since I’ve structured my playback configuration based on RAAT, it’s hard to use other software now.