This is actually a great idea. It is even compatible with having private companies run the system. The real issue is distribution (online code verification is trivial). Tbf I believe that a fully government-owned anonymous system should be the goal. The government knows you already, so creating a proof of age anonymous token should also be somewhat trivial. Truth is companies don’t want to forgo the potential profit in data mining, and governments don’t like the actual lack of control and full anonymity, otherwise we’d have this already worldwide

In theory I agree. In practice I have severe misgivings about directly incorporating government issued IDs into mundane online transactions.

I don't want "papers please" to be normalized. If the smart ID can do anonymous attestation of age then it can presumably also share various details with a requesting party. Next thing you know Facespace 365 is requiring you to provide your (attested) full legal name in order to register an account. I find that to be a highly objectionable outcome.

If things escalated beyond basic age checks that also adds hardware requirements. Would I find myself needing a smartcard reader to do anything online? The friction of needing to visit a bank in person seems like a feature to me.

What doesn't bother me is age restricted content guarded by a low fence. The bare minimum required to blunt the impact of something that appears to be analogous to an epidemic.