Crypto gamblers will naturally find it easier to withdraw winnings using Crypto, as They can be used as Trading capital or to deposit more funds, as crypto is faster than fiat.
This is primarily a matter of privacy. Users can withdraw their funds in cryptocurrencies far from the eyes of the authorities, even if they were first depositing in fiat. Using crypto has become more easier than before because of the variety choices of exchange/swap platforms that has become accessible to almost everybody.
Deposits with fiat require a Confirmation time of between 1 and 3 minutes. If using fiat, don't forget to click the confirm deposit button, otherwise your Fiat deposit will not be credited to your Account.
I think it is better to avoid using fiat in crypto-based casinos. Better to exchange fiat to crypto using one of the exchange services, then deposit crypto to the casino. This is safer because dealing with exchange platform in an issue about fiat is much easier than dealing with a casino.