Onehash does have this kind of feature but it's just an option for the bettors. If you want to register, it's okay but if you don't want to, you have an option to deposit anonymously and you will be given a certain bitcoin address to receive your winning. And after that, the deposit address will be given to you so that's how you bet without any registration. You are not enforcing your gamblers to use it but you are making their lives easier by providing an option.
Of course this is how Onehash runs ,and besides privacy is what people needs here thats why we all transferred here from the centralized world so we can enjoy our anonymity
If someone doesn't want privacy, he's free not to gamble with those casino's that guarantees anonymity or he can just not gamble at all. Data is becoming the crude oil of our generation and this is why some companies are mining data for the sake of their profit. It's all rotating now and everyone is becoming aware of anonymity and we all want it who are aware of it. While some who are not really aware of this, doesn't really care at all and it's fine for them whether they are secured or not.