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.
They don't need to negotiate with platform management because they can do it directly in many casinos. Or they have a casino that has become their favorite place to launder their money at the casino so they can easily play gambling and launder their money without any investigation. And yes, the casinos do get a good income from this activity and this is probably why there are a lot of casinos out there that are still able to stay in business. It is not easy to find money launderers or even casinos that protect this activity, so the regulators need to work hard to find them.