How would they pay for the infrastructure required to support all those users? I can't stand ads, but when I was younger, no way would I have paid for YT Premium (though to be fair, ads are much, much worse now).
Bandwidth transit prices, peering, and other data for for ISPs and the like tend to be highly classified (lol), but it's very close to $0. Take Steam for instance. They are responsible for a significant chunk of all internet traffic and transfer data in the exabytes. Recently their revenue/profit data was leaked from a court filing and their total annual costs, including labor/infrastructure/assets/etc, was something like $800 million. [1]
Enabling on site money transfers (as YouTube does) and taking a small cut from each transfer (far less than YouTube's lol level 30% cut) would probably be getting close to enough to cover your costs, especially if you made it a more ingrained/gamey aspect of the system - e.g. give big tippers some sort of swag in comments or whatever, stuff like that. It's not going to be enough to buy too many [more] islands for Sergey and Larry, but such is the price we must all pay.
[1] - https://www.pcgamer.com/gaming-industry/valves-reported-prof...
Let me pay usage based, with full transparency in hosting, infra, and energy costs. Like a utility.
Subscription services are like hungry hungry hippos, you give them $10 a month and next year they want $100.
I honestly think if everyone starts paying, it will only make them remove the free tier quicker. I think society is better with youtube free, even if ads are annoying.