As a Spotify user, I often wonder how much they're constrained in their choices by their contracts with music publishers. As an example, the fact that you don't have an option to downvote a song - ie, signaling that you don't want to hear it - is such a feature gap that I can't believe it's there by choice.

I wouldn't be surprised if creating a truly great AI DJ was also hindered by this kind of legal shackles.