my reason only data security and complicated,
I don't gamble too often, so I don't feel I need a casino site that needs KYC,
there are now many good casino sites that don't require KYC,
so, don't mind the casino that requires KYC.
There are incidents that a non KYC casino would require you to pass it when you are about to withdraw. If they suspect you base on the history of your activity within their casino, they have the rights to do it.
I usually try to avoid KYC casinos, but there are sometimes require to have a process like this one.
There are a lot of people who abuse faucets and rewards which is a loss for the casino, so there should be some measurement that can eliminate those abuses.
The casino house needs to implement that requirement to counter those abusers and in order to protect their business, a lots of people loves to enjoy playing anonymously and if they can continue doing that they will not process and provide any important information about their personal identity. It's about privacy and there's still lots of people who wanted to keep it.