From my observation, people are annoyed with KYC if the casino ask KYC during registration and when you withdraw the first time.

The reason is, people want to observe your casino first, hence they don't like when they get asked to complete KYC during registration.

Then the second, people don't like that because it's like the casino trap them, they can make deposit and they can't withdraw.

People are fine if the KYC are when they want to make deposit or at other times.