I don't know if you're referring to how it works where you live, but in regulated Europe you have to pass KYC
I'm talking about the same casinos and paid sites where multi-accounting can be beneficial and work on the Internet. Providing documents that are sold and bought in batches on carding forums will not play a big role, without the uniqueness of the user's system. Anti-fraud analyzes the characteristics of browser fingerprints and, even without registration, can understand whether this user has been on the site before or not.