But it would be better to use multiple languages for their site so people who don't understand Chinese can see the gambling games. It can also attract people who want a new experience with Chinese-style gambling games. In addition, they can have the opportunity to have members from outside China and develop their site even more. Or maybe the casino team just wants to use Chinese and doesn't want to get into trouble if they use multiple languages.
Yes, it will be always an advantage for having multiple language for a platform like casino/gambling.
But if the platform only have particular target market, then having such feature
(multiple language) doesn't make any sense so better to stick what they have considered.