When Apple dropped DRM from their music downloads it was a great day. Suddenly one could download music for a competitive price legally from the internet and use in all the ways. Putting it on my mp3 player or my media server and create a backup, which I can trust to be usable even a few years. If a new audio standard comes by I even can re-encode and keep it.

Meanwhile however we have Spotify and are back in the walled garden.

Movie industry unfortunately went directly from physical media (with stupid DRM restrictions - my favorite one is that on a "legal" DVD player I am forced to watch a short sequence on how bad pirates are, on my "illegal" DRM free player I can skip that part) to streaming. Making sure I don't "own" a thing and making sure my computer runs software limiting what I can do with my computer.

In the legal sense, buying from iTunes is actually "buying", while you do just rent access (similar to a Gym membership) when you sign up for Apple Music or Spotify. I don't blame them for using DRM for music when the user needs a perpetual license to continue listening to it.

Maybe "non-redistributable" instead of "non-copyable."

I don't disagree with your assessment, except I'd say DRM doesn't exist to restrict the machine - the goal is to restrict the user. Which is necessary, when users aren't trustworthy.

But I'd disagree that DRM doesn't serve you a purpose. It serves the purpose of establishing trust and enforcing conditional exchanges of information. The alternative, like you imply, is no communication, or communication through a different medium that doesn't involve your hardware at all.

These kinds of reductionist arguments don't hold much water in the real world. Using arguments like this you can justify ransomware--after all ransomware is just CPU instructions running on a computer. That is what computers do is run instructions. Therefore, it is totally okay if the instructions happen to encrypt the entire contents of a disk and prevent the user from accessing it until they pay money.

Here in meatspace, we have this notion of ownership and property rights. DRM is a mechanism to protect those rights. They may not be perfect, and they might not always make much business sense but that is their intent.

The ransomware doesn't do what I as owner of the computer want and nothing which serves me a purpose. The comparison doesn't work.

If you look for a comparison: DRM is like a book publisher printing books on special paper which prevents copying and which can only be read in a specific angle so I can't easily take notes containing quotes from the book. All to protect those rights. (Edit: actually that example is missing a piece - you need special reading glasses to be able to read it, that's what DRM is doing on my machine)

And yes - Napster was an issue for the music industry. Suddenly their content was there for free and easily accessible. But then there was Apple, giving music away DRM-free with even better usability and for an acceptable fee.