I made a PayPal account when I was 17 and used it happily for 12 years. In 2021 (being almost 30 years old) I got a payment from US (I'm in the EU) and had to provide ID to PayPal.
They figured out that I made my account a few months before my 18th birthday and permanently locked my account.
It seems all of this is arbitrary more or less random bullshit.