If you want that you get an OS that specifically supports child mode, you don't mandate all OSs default to having a child mode. The reason you don't do this is because when it's in place the default will be if you don't want to prove who you are you can't go anywhere on the internet except the most milquetoast sites (with no user created content) and the worst of the worst sites (that ignore these rules).

If I want to bash the government I don't want to have to choose between giving my id and going to terroristforum dot com.