I don’t think that would have worked. Parents buy phones for their kids since the kids can’t buy them. What would the choices be? Give them a phone or not give them a phone. I don’t think society is ready for that kind of choice anymore.
Or give them an age-locked phone that tells the websites it belongs to a minor.
But its already the case now! As in if you buy an sim now, it comes with filtered internet by default. its been like that for years
You have to phone them up/log in and request the block to be removed.