Honestly it's the social aspect. Everyone I know uses Spotify, so sharing playlists and tracks are super easy. I know there's converters out there but I can't be arsed to do that every time I want to send or receive a link. I've also got some shared playlists between friends we all contribute to. At social gathering I can turn on the party mode or whatever it's called and let people add stuff to the queue. The big one though is I've got a few friends with really good taste. I can check in on them from time to time to see what they're listening to right now. Found a lot of great stuff this way.