You need a Google account for living a normal life, or perhaps an Apple account but that's about the extent of your options. I'm sure Google can do the math on how many principalistic people are not going to watch videos with ads anymore if they have to log in for it. Most people are already logged in because they needed an account at some point anyway, so the vast majority of viewers wouldn't even notice. Kicking off adblock users won't be a financial loss either, so it's only about the group that was logged out (probably a tech savvy, privacy-aware audience) and didn't use ad blocking (tech savvy privacy people that watch ads? You can count that group on one hand)

I hate to say this because I'd be affected but that's the math I would expect them to use. The only counter argument I can think of, why they might care to keep freeloaders there, is the network effect