Do you actually manage devices for kids? It's a massive pain fine tuning all the controls on Apple, and the only way to really be sure is to completely ban the web browser and the app store (and probably more things I have missed). Now do this for multiple kids.

Most parents can't be bothered, especially if they are non-technical and intimidated by settings. And so they give their kids unrestricted devices. I think I read the average first exposure to pornography is now age 7. I'm speaking from experience as many parents I've talked to have thrown up their hands because they can't keep their elementary aged kid from using the ipad all night, despite there being an extremely easy screen time fix for that very problem.

I am technical enough to understand how to do all this, but even then I encounter many bugs in the parental controls, for example one kid is able to use Safari despite my blocking, even though they are on an identical device to another child who is successfully blocked.

There are infinite content sources now, and it's not possible to manage them all 1-by-1.

All that being said, broadcasting device user age should be completely opt-in for those who want it, and not mandated for every customer.