There must be at least a good reason why casinos add stable coins. One of the possible reason is to gain more traffic and perhaps many of their players ask them to add it. Adding stable coins can be a trend in the future imho if the traffic on those early casinos who add stable casinos increase steadily or even significantly.

I found an article from playbetr about this case, just in case you want to read it for references https://www.playbetr.com/benefits-gambling-stablecoins