So, they wouldn't take a single-use debit card? Or a wire transfer from an anonymous account?
It is my understanding they might take a single use card, but the problem of fake accounts was serious. . . so they use credit cards to validate accounts guaranteeing adulthood. . . and reality of the account holder to assure they were not bots. Same with wire transfers. Age requirements are paramount. . . so anonymous is only allowed after validation. That requires a real, not PO Box address.