Actually that is kind of what I was thinking about - the ability to build playlists from other services. I don't think any decentralised service can match the likes of Apple or Spotify in actually attracting big name musicians.
Lets say I'd been building my playlists for the past decade on a decentralised system, with the data on a blockchain.. Even if Apple or Spotify remove my accounts, the metadata (Name, Artist, Album) etc, is independent of Apple or Spotify. I could then plug it to Amazon, say, and still have the playlist be valid.
I'm not sure what the user experience would be like though as Spotify for example only allow 30 second song previews with their embedded player so you would still need to use their app. If there was a way to import playlists then it would be achievable but I am not sure that's possible on any of these services but I could be wrong.