Stable coins also have a stable transaction fee, especially if under erc20 tokens.. I guess altcoins with cheap fees are still favorable, especially for gamblers with small bankrolls in gambling.
Stablecoins especially those that use ERC20 platforms will really need very high fees for transferring. At least, we need more than $10 commonly when transferring stable coins from an exchange to others or to the gambling sites.
So far, if there are more altcoins that have lower fees, gamblers will prefer using it.
Some that are probably favorable are likely XRP, XLM, and also LTC