Don’t get me wrong, I’m all for privacy. But between setting up the birthdate when creating my children’s local account on their computers, and having to send a copy of their ID to every platform under the sun, I’d easily chose the former.
I’d even agree to a simple protocol (HTTP X-Over-18 / X-Over-21 headers?) to that.
Because parents are responsible for stuff their off-spring does and the government should not be needed to do that.
At the very most, provide tools to help parents (e.g. on device filtering etc. or require companies to provide APIs to facilitate the same goal)
Other than that: Fuck off of my phone.