I didn't say you hadn't got a physical copy. I said without one you're at the mercy of the company. Lots of people are moving away from physical media and I think it's a recipe to get ripped off.
Depends. If you know what you're getting, you're golden. I've 'bought' TV series before on amazon prime, but I know I'll only be watching them once. I would complain (and get the credit card company involved) if they went away with a year or so, but I have no illusions I'll be able to watch them in 5 years, let alone 20.
I pay for spotify, I don't own music any more. Got some old CDs in a box in the garage from when we moved house, but the only way to listen would be to put in the blueray player.
I believe in the US it's illegal to rip your dvd or blueray, but it isn't in many countries. If you want a digital copy to survive, the best bet is to create it yourself. If that's illegal, contact your local government representative to change the law.