Casinos can use both functionality and corporate branding but there are times when, when they want to buy a domain name, the price for the domain can be very expensive because it may be a premium domain name. So if the casino wants to stick with the company brand, they have to be prepared to pay more. If the company is a big company that has a lot of money, it will be okay. But if the company is small, then it is not worth it and they should think about choosing another domain name.
Hmm... well, I confess that this is also an important variable that I didn't mention.
I believe that the domain name can be a differential, not to mention that, depending on the domain, it can become more expensive, but on the other hand it can bring benefits and visibility to a particular casino that wants to have this differential.
That is why we have always been on the side of the functionality of the casino take for example even if a casino can pay for an expensive domain and get a unique branding but lack good features the casino will still definitely underperformed.