Subscriptions are a bane. It's the easiest way to make money these days and you can see it leaking into everything. It's no longer pay for what you use, but is now pay a fixed rate (and sometimes an additional cost for what you use)
You can see it everywhere. In cape town you got 'access to electricity' subscription like service.
Music has gone that way to, you no longer pay for the music you want but subscribe to a service.
I see this trend in the UK. It's no longer buy flea treatment, you subscribe to it and it's shipped to you. Same with the vet. Once off visit is 2x the price of a subscription to the vet where you get quarterly 'free' visits on your yearly subscription.
Even lawyers, ie. LegalWise. Expect more of type of thing to come around as it makes good business sense and profits (don't forget to subscribe to checkers 60 plus!).
It's not surprising that youtube would want to press this, it's be most stable way to keep an income without being at the whims of advertisers.
Youtube has a bigger problem though. Storage costs only go up as millions of videos are uploaded. Processing costs go up as well, not to mention the anti-copyrighted machine getting more and more content to match onto as studios produce more content. It's costs will always be going up. You'll find ads or 'better quality with premium plus" will eventually follow this path. I also think they might do what microsoft is doing and start deleting accounts/videos/data that are inactive.
We've already seen google do some sneaky things with gmail now sharing google one storage (where in the past, gmail was unlimited storage)
People can argue that it's not much, but when you start adding up all the subscription enforced these days (disney+, netflix, hulu+, amazon prime, checkers 60, xbox gamepass) it starts to get very expensive very quickly. It's a hard sell to change from free with few ads to paid/many annoying ads.