[m-p-3]

I don't have Android Auto but I can at least control my phone media playback through the head unit and the steering wheel controls over bluetooth.

I suspect this was mainly for people who only have the ability to send audio to their head unit without actual controls in some older cars.

[bonestamp2]

That's one use case. The other use case is people who want a dedicated Spotify display in their car. It's especially nice in a new car because you can have your Nav or something else on your car screen and have a second display for your music. Yes, you can also use your phone for that, this is just another option.

[nemothekid]

I think it was more so for people who want a dedicated spotify app - as in they want to go through their likes, playlists and radios without using their phone.