I suspect you don't realize it, but you explained the answer to your implicit question quite well. When I choose to purchase a movie, album, etc. in digital format (I don't do it very much but I have a decent number), and download it to my computer/phone/drive/cloud/etc., I own it. It is available for me to enjoy as long as I have a method to play it (basically, any device in the world that has a port and speaker or two (or more). So what you say about ownership is wrong.
Yes, if you choose to stream it (and for most songs/movies/etc that's all you need because once is enough) you have invested nothing and you of course own nothing and the owner is free to act as an owner. But that's apples (no pun intended) and oranges. Certainly you do not think you are entitled to think of something you did not purchase as owned by you. And regarding your friends who jettisoned their CDs when Spotify became available to them, as did I, did they not (as I did) back up those CDs onto a computer/drive/etc before tossing them? Where I come from, that's on them. [Not to mention, there was no requirement that they get rid of the CDs even if intending to rely on Spotify.] They could have left them where they were.]