This makes the tech companies the decision makers over what is suitable content for children. But this has many problems. A big example is that some people are more open about sex than others. I'm reminded of a scene in an anime of a father in a bath with his daughters, normal in many cultures, deemed perverted by many (particularly christian US residents). Also here in the the Netherlands, a pretty open society when it comes to these things, we have parents complaining about books that show genitals to kids, even though they'll see them when they look down.
This is a hard problem, from about 0 to 18, kids go from being, well, kids, to being expected to be full adults and are expected to be able to deal with every liberty, every temptation that comes with it. There is no single best path to achieve this.
I want to educate my kids about sex, about alcohol, gambling, drugs, I want to teach them that the internet is a source of many good things, and many bad things. I'll make arrangements, determine the suitability of online materials, and will set boundaries together with my partner, thank you.
