We've tried this before. In 1997. https://en.wikipedia.org/wiki/Platform_for_Internet_Content_Selection

The push for this form of age verification is to "close the loop" of strong identity between a physical person, and online content access. And unfortunately, all the relevant parties are aligned on this one:

• Site owners want to prevent non-people AI from accessing their content
• Authoritarian leaning governments want to track and control who gets access to what, and who can even make content available in the first place
• Ad Companies want to make sure ads are being served to real people
• Operating system vendors can kill open source by ensuring this is mandated at the OS level, in a non-bypassable way, so signed/TPM/closed source nonsense.
• Parents who don't understand the technology enabling this but believe that this 'protects the kids' will also support it.