A Casino Business Owner should have good knowledge about his clients. Even on any gambling platform where KYC is not mandatory, if anyone looks suspicious, they will be requested to complete KYC. However, there are some casinos that insist on KYC from the start. Especially when those casinos are licensed by the government they have to fulfill mandatory KYC. However, a casino owner may request to get this information at any time and users bound to provide it.
You're don't know if there are few casinos which will never ask your KYC even you're breaking their terms, conduct illegal activities, cheating etc, they will directly terminated your account. These zero KYC casinos are: BCH.games, Bitvest, Freebitco, Betplay, Bitkong etc.
Gambling in zero KYC casino is possible, but majority of people are done wrong thing by not read the whole terms of service of the casinos.