That will be a choice for the gamblers to register in that online casinos because they don't have to send any document to play gambling. I see that many gamblers don't like to send their personal information, and I don't like too, because we only want to release our stress by playing gambling and while we are connected to the internet, we spend our time to gamble.
We consider gambling as a way to have fun and not for making money and that is why we don't need to do kyc. But if we want to make a business, then I think kyc is needed because it will give more trust to our customer.