Then why wouldn't the owner change after verification? Maybe they should verify every day, just to be safe?

Such nonsense just ruins the Internet, maybe we should find better approaches than "yet another banner": accepting cookies, accepting privacy policy, verifying age, registering, logging-in, etc. all to watch some dumb 10 second video... Yet, porn and violence are to this day still a Google search away. So, what is YouTube exactly trying to stop here?

You mean every time a video is started as well as after every ad, right?

And drinking a can of beer for the camera proves you are 18+ without revealing your identity. I think we have something here!

That makes little sense. Does this require reverification every time you log in? After all you can't simply assume the owner has never changed.

If the verification has never been done, and to comply with any regulatory requirements, they will likely perform the check once. Just because your account is 18 years old is most likely not going to pass various regulations which they need to comply with.

Eventually, they could use the front side camera and do continuous face-ID style verification. So no getting mommy or daddy to do the ID verification for you.

I think you could already buy this from China... Isn't this pretty much what is done for that online gaming service limitation?

No, the Chinese aren't going that far yet.