> You remove kids by default (no credit card/bank card

Children have parents and many of them will shell out thousands of dollars a year so their kid can buy Fortnite skins. I don’t imagine a credit card requirement will keep kids off of social media.

For the purposes of addressing some of the data privacy concerns, I think it would be even easier to just restrict the collection and/or sale of personal information. Simply charging for the service doesn’t prevent or disincentivize companies from also selling your data.