I agree with the others have said that they Should have value. I think there is no point in doing that because there is no thing dedicated for gambling except the chips that has a corresponding value. Maybe the acceptance of different coin could be a better option.
If you Have many coins that you could gamble chances are you would have more customers, Especially if that time has a lot of users in it.I see a lot of gambling sites that integrated exchanges To make players easily convert to whatever kind Of coin they want
It has become a fashion like everyone want to have their own crypto hence why not a casino ? Being useful or convenient are not a constrain but I guess most gambling houses may come up with their own coins dedicated gamble with them. This fashion has already started with many crypto exchanges and it might be a time for casinos to copy that useless idea.
Basically I hate the idea of having numerous altcoins which are having repeated concepts backed and not having any value in rest of the world. As an innovation to have a common border-less momentary system, we have bitcoins but it seems we are again going back due to such purpose specific coins.