Spotify is on the best way to become the Google of the music industry. They're doing alot of things right. Not sure if it's the best decision to sell now but i guess the people from warner know what they're doing.
That can be a double edged sword. They can also kill products that are losing money. Apple does not give away much for free. If this is a loss leader I don't see them keeping the service.
I don't think Apple is making much money from Maps, and yet here we are, they keep investing into it. If Apple drops Apple Music, they don't want Spotify to come knocking at the door and say: pay us or we will discontinue Spotify on iOS. Much worse scenario: Google buys Spotify. Apple has been relying on Google Maps before, I don't think they want a re-run...