How naive. Spotify playlists are now sponsored, so if they know what music you like and can predict what you will listen to in the next few days, they can offer playlists that you will likely play.

When I played music using iTunes or MPD, it would never take my list of favourite songs and then try to predict which sponsored playlist I'm most likely to click on. In exchange for access to music, you're giving up your own data and then not being able to easily replicate your music library elsewhere.