[popcornricecake]

It's the internet. There are no borders and there is no mandate to follow any consensus. Stores may not want to sell cigarettes to children, but e-stores safely hosted in some remote country do want to sell them nicotine pouches and vapes. With a protocol that makes age information always available to websites they could hide their intentions from adults while actively targeting children.

[Ajedi32]

IMO you could have some mechanism by which websites could have content certified as child-safe if they agree to adhere to certain standards. (And thereby make them accessible to child-safe devices, which would otherwise default to blocking content which doesn't bear such a certificate.) Adult devices would not implement those restrictions and would therefore be unaffected.