BTC and ETH should be enough since you could anytime make out some direct conversions into other coins if you wanted to and those via exchange but it would be always better to have multiple options on the
coins that you could possibly able to make use but come to think that not all platforms does have those internal fast swap exchange from coins to coins which means that whenever you have deposited TRX
to the site which means that you would really only make withdrawals via TRX.There's no way that you could swap on in between.
I also think that if casinos use BTC and ETH, then this is enough for those players who prefer to play using cryptocurrencies.
The fact is that all kinds of altcoins allow, of course, in some cases, to reduce commissions or even slightly increase the speed of transactions. However, these circumstances are not very important for players who use fairly large amounts.
And as for the players whose deposit is $5-10-50, then such players are not very interesting even to the largest casino, and in particular to such a large casino as BK8.