So every time an exchange asks me for documents to withdraw, I'm being extorted? .
most known exchanges, make things quite clear.
Take Binance for an example , they literally tell you that if you decide to withdrawal anything above 2BTC per day, you will need to provide a,b,c documents.
Wrong. You are mixing up normal vs. irregular situations. Once you hit some random trigger, you may be asked for extra KYC even if you are fully verified already. The best you could ask for is that Casino's clarify in what cases KYC would be requested. Other than that I see this witch-hunt leading nowhere unless you want to go after every single exchange as well (some other services probably apply too) and in that case I wish you best-of luck.