Actually we can't avoid this to happen since there are so many circumstances like you win a frequently or there's a lot of money involve in that win or there's sudden change of activity and the casino want to verify to know if the account is maybe safe. So its better for gambler to stay away on a casino claiming that they would not ask KYC to their costumers since in long run it will happen and its feels like we deceive. More worse if they turn into scam that's why maybe better to look at it as red flag then go to reputable casino which is transparent on their KYC process since they can offer more secured platform and that could give us less stress.
I think most of these casinos are aware that if they request for KYC upon registration, they won't get much customer so instead of being transparent on their KYC policy on registration they would rather request for KYC upon withdrawal of huge funds when they notice an individual has won big money. This might be a tactics by most casinos to attract more customers to patronise their business.
That's why it's important that before you register with any online casino you should do well to crosscheck their terms and conditions carefully and be sure you check if they got any KYC policy that’s not very transparent and would still require it along the line, then it's best you flee from signing up with them. Just that some individuals are very carefree about going through terms and conditions of a site before registration.