Interesting concept. If I understand it correctly it didn't truly let you own the stuff that you bought. It instead gave you a proof-of-purchase allowing you to stream your purchased content on different streaming platforms (like Netflix, etc) as long as you have that one proof-of-purchase. However, if the platforms remove your purchased content from their catalogues at any time, it would be gone. So you're right, almost but not quite like DVD.

I wonder why the notoriously copyright-obsessed music industry allows retailers to sell digital copies (and high-quality ones), while the film-industry doesn't.

I knew the moment I saw these stickers on my dvds that the links to the online content would never last. This happens to me with textbooks all the time - oh great - digital searchable access to the content, but then after awhile the hosting site goes under or changes hands and it's never easy to just download the content. Whether I purchase a text or not. I always try to find a pdf version of it that I can just save. No one is going to let this legally happen with video in any kind of format that you would be satisfied with. Pirating is often the only way to really own useable digital copies of media. Im at the point where I would prefer the simplicity of paying a fair fee to easily download an unfettered mkv file, but I don't see that becoming a real thing.