They already do, go use the latest version of yt-dlp to download like 20 videos from a channel without passing cookies, and a very short time afterwards, everything at your IP address will be blocked from watching any videos unless you sign in.
I download a lot of things from youtube using yt-dlp. So far I never had any issues with getting ip-blocked. In contrast, Instagram ip-blocks me very fast when I use gallery-dl to download a profile. I usually turn my modem on and off to get a new ip address.
This is a thing already. "Sign in to confirm you're not a bot. This helps protect our community.", needless to say it applies to people and not bots, and does nothing to protect the "community". It's only going to get worse until people stop giving money to Google.
YouTube has blocked access to videos considered to be "adult" (not porn but anything vaguely risqué) in Europe without signing into an account and performing credit card age verification for five years.
This is less of YouTube being YouTube but more of EU being EU (Article 28b of AVMSD), although I do not know if YouTube requires credit card verification in other countries (I know that YouTube now requires sign-in for "adult" videos basically anywhere, but how they implement them exactly is something that I do not know).
