To be honest, for the "average" prime subscriber, the included Amazon Prime Music would be more than enough for them. For people really into music, Spotify or Apple Music are still the better options.
Yeah, I'm dropping Spotify and using Amazon Music again. I recently checked and there was only one album that they don't have, that I normally listen to. Cheaper just to buy that one album then pay even the $5 student rate I still pay with Spotify.