I haven't been to prison personally but from what I have seen in the movies and read from articles, I can say that its definitely not for the weaklings.
All kind of nasty shit happens in prison and gambling is just one of them. If we are not strong, we won't be able to survive longer in a prison.
Those who are addicted to gambling will have a hard time in prison because they won't have much to offer and might often end up in fights to due to non-payments.
The prison in as much as it is very necessary, is not supposed to be meant for everyone whether you're a weakling or not. The experience in the life of a prisoner is a really tough one. It is like the punishment of someone who's trapped in the hell. Every moment in the prison is followed by sadness and anguish. It doesn't allow you to have access to the outside world.
You suffer from being caged in one place. While all of these experiences seem like a nightmare, some elements of people really deserves no where but the prison because of their atrocities. In my country, the prison has been renamed to now carry the name of a correctional centre instead of prison because it is supposed to be an environment where you are kept out of the outside and trained to be a better person. I don't think People should be denied gambling in the prison because it is a correctional facility that does not only purnish people but also to correct people so gambling can be allowed in the prison but highly regulated so those involved in it do not do it any how.