If research is conducted on this, I am assuming that crypto gamblers will be much higher than the numbers of players using stable coins, the reason is because many people that preferred Fiat are using centralized local casinos to gamble but for the many of them using the only crypto casinos, they are betting with crypto.
Take look at any casino that has a ticker with the latest bets, high rollers and so on, barely any Bitcoin users and a lot of USDT, Bitcoin betting has decreased when the fees were through the roof and it hasn't come back again, poeple like that 1 usdt =1 usd, the fees are low, transfers are nearly instant and they really don't care about anythign else, privacy matters close to nothign these days and anyhow, what privacy when you complete KYC after KYC with the worst and worst requirements these days.
It's a win win situation, they're trying to minimize the possibility of them losing when there is a decline in Bitcoin price and the gambler too. Imagine depositing $100 worth of Bitcoin and waking up the next day to gamble and it's now worth $80 due to volatility.
Volatility goes both ways, it could easily be worth 120$ and if someone were able to predict a 20% they would be making millions from shorting it rather than gambling.