This should not be a big issue now because almost all of the casino offers more altcoins to gamble with along with bitcoin. If anyone cant afford the high fee of bitcoin or ethereum, they can use dogecoin or litecoin to deposit and gamble. Also after bitcoin have reached all time high, people prefer to gamble with cheap altcoins more often than with bitcoin.
Yeah it is a firing issue right now; I love the gamble only with bitcoin but unfortunately I am not affordable to transact bitcoin which leads me to switch over to some other coin like tron/doge for my gambling purposes. I really hate to do that still I do not have any other options. Because, for calculating profit or losses from my gambling, I am comfortable with bitcoins and not with any of altcoins. Moreover I am just gambling in terms of BTC value are not in fiats value which might be the reason why I'm not comfortable while gambling in altcoins.
This is kind of situation we need to face and move on because even after adopting segwit, we are unable to solve high transaction fee problems. I am seeing this is just like another opportunity for saving more bitcoin because nowadays I am gambling in altcoins which helps me to save relatively more money than if i gamble in bitcoins.