Take note, Casinos will ask or demand a KYC if there's a big winning involved, is this one of their ways to scam their players?
It is a debatable question, no matter how hard to accept this fact it is still one way for casinos to verify user identity. I personally don't deposit as much as the amount that can be subject for KYC verification and it is not safe to share personal documents with third-parties. The same idea is true for some crypto exchanges as well. Maybe they use this method to scam big winners since it is rare to see complaints about the casinos which block user accounts that lost big.