It will always be crypto and even in the near future I didn't intend to use fiat in online gambling. One explanation is the rule. There's no specific law in our country regarding crypto gambling, so I'm pretty safe from regulation, despite how much I've played or earned. I'm still unfamiliar with using fiat gambling site. What if they need KYC that I'm ignoring or they're unlawfully operating that might smear my clean reputation. So when you have online gambling operation, choosing crypto is the best thing to do.
Rule? That does not explain anything and why you want to use crypto currencies. Yeah, since there is no specific laws, you might end up doing something illegal in an unknowing way unintentionally. Too bad, it is no longer safe from regulation. Most of the online crypto gambling sites are now being forced to collect user information and make users go through KYC due to regulation.
You should always read the terms of service first of a casino before you start playing over there.