Any land based casino of an acceptable quality level has chips of its own, and those chips can only be spent on the casino premises. Also you can exchange the chips for fiat currencies exclusively inside that particular casino or, in some cases, inside a casino belonging to the same chain, but nowhere else. So, there's no problem with having your own coin, and it has been practiced already by many online gambling sites, as you can see from the comments above.
Those chips were well demonstrated in final scenes of the movie hangout part-1.
Here is the wiki article on those casino chips :
https://en.wikipedia.org/wiki/Casino_tokenYes, it is already in practice so not a big thing for any gambling houses. But, we need to consider the big differences between having a dedicated cryptocurrency and having such tokens.
These casino tokens are just to representing local fiats and its value is not depending on the performance of the casino but it is being used only for the purpose of easy handling of fiats whereas having a own crypto is completely different thing as its value may fluctuate as per the revenue generation of that house. Or, house may go for stablecoin kind of crypto to give gamblers some peace of mind but in that case it again sound like casino tokens.