Stakes can ask for KYC any time they want. So, be ready to Submit KYC if they ask you to verify. I have been there for a long time, yet I did not KYCed there. They did not ask me, maybe because of my gambling habit. It depends on various factors, including what games you are playing, on which market you place your bets, and how much the amount is. If you place bets in Sportsbetting and play 3rd party games, you will likely trigger KYC. Also, Sometimes they ask for KYC if they are suspicious of your activity like arbitrage betting, Random IP change etc etc.
And not just Stake, even sites that are saying that they don't they can ask for KYC eventually. So always assume that Casinos and exchanges will eventually ask KYC. Casinos promising that they don't ever ask kyc either don't use anything even related to stablecoins, or are just promising something they can't keep. Because it's really not up to them if they want to comply with AML laws.
Can you please refer me to any example where a casino promised that they wouldn't ask for KYC, and then asked for KYC? I don't think it's happened before. It it's happened, those casinos should be exposed. Any Centralized exchanges will ask for a KYC. But I don't think decentralized exchanges need your KYC. Most of the casinos ask for a KYC because they are somewhat regulated casinos. They have licesnce and the license provides and game providers ask them to get KYC from users. If you find a casino is licensed and promised not to ask for a KYC, they are lying. Moreover, if they promise not to ask for a KYC and then they ask for a KYC, bring them up and you should expose them for doing shitty things.