KYC analysis isn't free. You either hire a KYC manager or work with a KYC verification company with whom the operator needs to pay for each verification. Casinos need to balance their financial sustainability and the needs of their users in order to stay competitive in this market where bonuses are becoming increasingly generous.
Most fiat casinos, especially those being required to conduct KYC when the player first sign up, can only offer less generous bonus and demand higher house edge partially for this reason.
If it is a scam site, KYC will be easily because they don't verify anything, just ask users to submit documents and steal those documents to sell for money. Difference between legit services and scam ones.
Your explanation clears many things, Coinbox1.
You raised an important point. Personally, I would suggest against submitting KYC documents to an operator you know little about. Always do your own research and check the license before doing it as I have heard of fake casino sites designed solely to obtain KYC documents for free and sell them on the dark web. If a "casino" has no valid license, no digital footprints, but asks for your KYC documents right at the sign up, then it is likely a scam.
The internet & blockchain world is a wild and free place, and we should all stay vigilant.