That should be depends on the information giving to the participants by the casino and the manager of presenting it. But frankly speaking it will not be easy to deal with that. That is why all casinos should secure their websites. And I believed every gamblers would be expecting refund from the casino. I have not heard casino hacked but I have heard exchange hacked.
I don't think I have seen any casino that includes in their terms of service that they will refund customers' deposits in cases of hacks. No matter how protected a casino might be, it is still prone to hacks. Former or present staff of the casino can compromise it. We would all expect refunds but from experience, this is not always the case.
I still wonder why big companies irrespective of the industry they're in don't have insurance for hacks when it happens. Why the platforms you called were able to recover customers stolen funds was because they had reserved for incidents like this. All casinos should have this too to preserve their business because it isn't easy to build back your reputation when it gets ruined.
Taking an insurance policy against hacks could be another means of covering these losses caused by hacks. With the backing of a reputable insurance company, the gambler's refunds are certain.