Bitcoin is the most used cryptocurrency in gambling, but in my opinion, if I were to gamble, it is more better to use XRP because of its sustainability and doesn't have too much volatility like Bitcoin, where you could avoid the high transaction fees. The reason why gambling sites preferred bitcoin is for them to earn a lot of money because of its high price fluctuations, for example a gambler just lost 1 bitcoin and cost $30 but after months or years it could double up or triple up, it is all about marketing and business.

Gamblers should know first the Pros and Cons of the cryptocurrency that they are going to use in gambling before started to deposit in a gambling site to avoid further losses in the future.