Comment by lokar

It's also important to understand that this is not a binary situation. You will never keep 100% of the kids from 100% of the inappropriate material. So it should be a debate about levels, and trade-offs.

IMO, the approach of having the large / popular commercial OS platforms ask you the birthday of the primary user on install (and secure that so it can't be changed), and then reveal the age (bucketed to a range) to apps. If you don't have kids, or care what they see, just put Jan 1 1900 (or have an explicit opt-out, which puts you in the last bucket). After that it's up to parents to parent.