It gives you the same currency in which you have placed the bet. So why do they need to worry about how much the price of bitcoin has decreased?
exchanges need traders and as we know the number of traders decreases in a bear market. Because of this, their revenue decreases and they have to stop providing services.
Casinos, however, have a different business model. It doesn't matter to them what the market conditions are because the gambler doesn't care because for many people it is an entertainment purpose.
Even if we put the FTX exchange aside for a second, there are many other exchanges that have died this year who didn't get much media attention as these were small exchangers.