EFF launches Age Verification Hub

Why don't we have zero-knowledge age verification?

One actor verifies ages - and they only need to do so once. Sites give users a key tied to their user account to run by their verifier, who returns another key that attests to their verified age encoded for that specific site, to give back to the site.

The site doesn't know anything about the user, but their user login info. The verifier doesn't know anything about what sites are being visited.

This would seem to address the issues, without creating the pervasive privacy and security problems of every age verifying site creating database of people's government id's, faces, and other personal information.

It also seems like a way out of the legal/legislatorial battle. Which otherwise, is going to be an immortal hydra.

I would trust the EFF to run something like this. Open source. With only one-way encrypted/hashed personal info stored at their end.

(I am not a cryptographic expert. But I believe mechanisms like this are straightforward stuff at this point.)

I think you're suggesting a centralized actor to verify the age of users which is problematic on multiple accounts. Practicality, privacy, enforcement, liability to coercion/corruption, and so on. This might be a wild take, but I think platforms could do a lot more to help with moderation to prevent child predators. Instead of just being okay with them finding outside avenues to converse with their victims through their platform, maybe use those algorithms to detect and prevent it in the first place, whether or not said child predators are whales for your platform or not.