I have not been to prison, but among the stories about gamblers I had to read that some guys went to prison because of their debts, and there they were asked to play cards for fun at first, and then this game drew them in and the excitement began to work, and they were already playing for money, losing everything. And they were forced to ask their family members outside to send them money to pay off their debts in prison, otherwise they would be killed. Therefore, many advise not to get involved with gambling in prison.
I have also heard similar stories, then first you gamble for fun, but then your opponent either cheat, or by force and threats forces gambler to change object of game from fun to money. All this is done to make a person be in debt, then this person is manipulated, which leads to debt increase, turning player into a slave. If I ever get into prison, gambling will be the last thing I would do there. I will do my best to find a less stressful time killer and entertainment.