But, do you know that it's not usually the same thing in every prison, like some countries, they will not allow drugs in the prison because if noticed, the boss in charge of the prison could lose his job and the prisoners involved would face more difficult sentence, even some wouldn't allow gambling. So, it totally different everywhere. I know that in movies, we see different things that might not completely happen in real life.
Movies and real life are different, but some movies are not just fictional but they happen in the real world. Gambling can happen in prison, especially card games are the most frequent kind of gambling they deal on, smuggling a card is not a difficult task to do. But the harm that happens while they gamble is much and i am certain that it will be what they do in secrete.