I know the pain being myself a gambler but there are lots of solutions for the problem. You can either play with coins like TRX or XRP which have almost negligible fees for withdrawal and you don't even have to wait for confirmations either.
If you somehow deposit BTC and now stuck in the situation then I have another solution for you, just visit this site
https://cryptogamblers.pub/exchange make an account and follow the instructions and you will be able to convert your Bitcoins into any coins supported by stake within minutes but at a small exchange fees. I am NOT promoting the site though, I used them and worked out very nicely for me.
Whenever I am playing small, I use this service and convert my coins to withdraw.
I believe if exchanges can offer such a big variety of coins and options, there should be some sort of method casinos might as well start with that too. Stake is leading in altcoin adoption and even they are not wide enough. For example look at binance and how much coins they do have and even the ones they have also have a lot of separate chains as well that is the great thing about it, because if you want to send USDT somewhere, you can do erc20, you can do trc20 and you can do original, if you want to send something else you have those type of options all over again.
Basically speaking we are in a situation where crypto could be helping casinos offer 100+ coins if they want to. But, when we are in a situation where even the leading casinos offer under 15-20 coins, that shows that casinos are not willing to put as much options as exchanges and maybe exchanges make a lot more money but casinos could at least try to get a bit more.