Some of the Gambling casinos I've seen are requiring its user to conduct a KYC (not mandatory but they said there's a chance or something) however my concern is that the gambling casino is not licensed are you going to trust this or not? Imagine winning a big jackpot and they asked for you to conduct KYC but they are not licensed.
Unlicensed casinos don't have a right to function, nothing to say about giving KYC documents to them, without doubt, you shouldn't do it. Personally, I wouldn't give away KYC documents on every licensed casino but would risk on those whom I trust and are trusted in the crypto gambling community.
It's easy to obtain the license and you know, a lot of licensed casinos scam nowadays, so imagine how poor scammer would an unlicensed casino be and also how bad employees they should have.
Better to try your luck in jackpots on trusted casinos. Usually, that kind of reward giveaways (when user registers and somehow quickly wins jackpot) are the sign of scammy action.