On-chain transaction fees are always one of painful experience for blockchain users including gamblers. It is similar to Play-to-Earn games on expensive chains like Etheruem ERC-20 chain and maybe Binance Smart Chain some weeks when BNB hit $500 to $550.
When there are lot of transactions then the fees goes up really high and players find it hard to afford specially at the ETH network because for a small transfer also you have to pay huge gas and big whales in order to confirm their tx pay double or more then average which boost the fees even more.But yes you can surely try it on weekends when there is less volume but it's open 24*7 so can't say it will stand true.
It’s nonsense to use ERC20 tokens to play on Duelbits because it automatically converts all deposits to fiat. User will just waste expensive gas fee if they will use ERC20 which is known for high transaction for gambling purposes while they can use other small fee tokens to deposit and withdraw.
Besides the difference in fees during weekends or peek hours is not that huge unless you are playing with a balance that is just the minimum amount to withdraw. Nevertheless user should not use ERC20 in general if their balance is so small. ERC20 nowadays are for whales user only since most of the tokens is available on different blockchain due to the existence of bridge.