Music is very personal to people. Very, very personal. It's not like Netflix, where a TV show appearing then disappearing later is not that big a deal. With music, if you lose access to a song you love, it hurts. Some songs, I just want to own. For the rest of my life, with no risk of it being "taken away".
Why can't we just have both? It doesn't cost ANYTHING extra to have both. You have to have the song on the server anyway. Simply let the user *stream* it if they have a subscription, and *download* it DRM-free if they want to buy that track. The cost delta to implement both is tiny. Hell, the music has to be encrypted for each user anyway to apply DRM for streaming; when you buy the track it actually uses LESS CPU power because the raw unencrypted data can be sent!
Not to mention, instead of just $10 a month, you're getting $10 a month + purchases from many customers, myself included.