The governments won't protect them either. The governments are the ones enabling these corporations to exist and facilitate harm towards children. Maybe they shouldn't be allowed to have those corporations.
They are doing something which is not a solution but can fake being a solution, so that the masses will accept it. An actual solution would be to regulate these social media, to prohibit addictive and manipulative algorithms.
Maybe OS vendors should stop trying to sell ads and instead fix their operating systems so that parents can responsibly monitor their children's online activity in a way that promotes both parental responsibility, and children's human rights ... but of course, that would require OS vendors to stop selling ads.