UNICEF started accepting crypto currencies for their donations too. Pretty sure gambling whales are donating a lot from their winnings. I experienced donating but only small amounts. Most people lose rather than win in casino houses that is why donations aren't that popular from gamblers.
i just read that articles about that but it seems right now we can't do that because i already try it and the payment we can use just Credit card/Paypal
if they already implement this feature maybe many gamblers will donate a few of his winning?