Therefore, it has no effect as long as users can deposit BTC and play with its fiat value, which is pretty much best practice on crypto casinos.
Anyway, if they really remove BTC as deposit/withdraw method, then it's their loss as we can pick other hundreds of crypto casinos to play.
It is true that a lot fewer people are seeing Bitcoin as a usable currency any more and it is becoming simply a traded commodity. I guess if you are a pure speculator then it is better as a commodity like Gold, which is much easier to move around and has a very liquid market of buyers. However volatile assets like Bitcoin can be a bad thing (or a good) for gamblers depending on which way the price moves. The general trend has been up for a long time now, so if you bet money and lose - you lose even more as the price continues to rise after you handed over your crypto to the casino. It'd be better to bet in something like USDT instead that you know has a fairly reliable value that will not fluctuate anywhere near as much.