Criminals may well launder money through casinos. To do this, they need to negotiate with the management of the gambling platform. It is risky, but money laundering through online casinos is a common way for those who are engaged in illegal activities. The management of gambling platforms receives a good income from such shady activities.
I think money laundering if done is done through mixers more than is done in casinos although people may use casinos for small amounts which really is not considered money laundering.The casinos may serve a good purpose in making your coins anonymous as you can deposit to them through a wallet and receive money in a brand new wallet that you create and the tx id is different because the money is coming from a wallet of that casino,that is the maximum people can use casinos but criminals to launder money through them I find it hard to believe.