That's a good reason to prohibit it but does it stop people from gambling, no it doesn't and that's how it's always going to be. When you prohibit something, it only make people want to do them more. I think there should have been better ways for gambling to be discouraged without forcing people to stop through prohibition. Make it allow and see how lesser amounts of people will still be gambling. Soon as they see that it isn't favouring them. They'll look for other things that they can do for entertainment or for making money because that's also the reason people still gamble even in prisons. I don't have personal experience of gambling in prison but I have seen them in movies and it isn't something that I find entertaining because people die from this.