Because many times casinos that say they do not ask for KYC, then when someone wins a lot and wants to withdraw the funds, they ask for KYC for that person because they know that this person has a high chance of not doing so, and the casino keeps the person's money.
Its deceptive for a casino to have something like this if they are serious about their no KYC offer and there will be no point in the time you are playing or when you want to withdraw that they will ask for KYC gamblers will then trust their platform.
If they will ask KYC at some point, then better not mention the no KYC offer. Gamblers do not want to be deceived.
Based on my experience and what I've read in many complaints, casinos like this have hidden agendas, so its better to not trust what they offer and just read the terms.
No KYC what most new casinos mean by that most time is that they are not going to ask for KYC verification at the time of your account creation and at that you can play for as long as possible without KYC demands but in their terms of service, but that doesn't mean that they will not ask for KYC if and when the account activities become suspicious.
So we should not expect a total no KYC casino to gain much popularity and if you are looking for such a casino that you don't need to do KYC at all then you have to look for a decentralized casino but even st that you still have to deal with the issue's of low liquidity or traffic on such fully decentralized casino.