I believe it is an FTC regulation that if the site is open to those under 13, the owner of the site has to make certain disclosures and reports, so all the companies running the sites just require the user to be 13. They will not set up an account if you don’t day you are at least 13, so all the kids lie to set them up.
I regulated my kids and they did not have accounts until they were 13 (and one is 10 months younger than her sister, so it was torture for her) At the time, we had one family computer so pretty easy to regulate. I also had the rule that they couldn’t add any friends who they had not met in person. The younger one added a friend of her sister’s, but she hadn’t met him in person so off he went. They didn’t even have phones until they were 11 when Santa brought them, but even then they were flip phones with minutes purchased on a card so very limited.
My FB was hacked in August and I haven’t been on since then. There are a few things I miss but I’m trying to decide if it is worth it to rejoin. Just today I was told to follow a group on FB and I had to tell them I couldn’t. Old school, I know. I’ve never done Twitter or Insta=anything. I still read the paper that is delivered to my house every day too.