Agree, but at @Tom_Glorieux indirectly points out, one useful area where Roon could integrate with Spotify is at the Playlist level.
Effectively using your Spotify account details within Roon — much like you’d do in Soundiz, SongShift or TuneMyMusic — solely for the purpose of importing Spotify playlists into Roon and sharing Roon playlists with non-Roon users. Without you having to leave the Roon interface.