If more prisons had that system, you would see a lot less criminals. I remember reading that prisons used ot have convicts do sewing as well, making them work and putting htem to good use. They shouldn’t sit idle and allowed ot be converted to Islam or any other loony religions that are gaining a foothold with these people.
Into the 70s Michigan Southern Prison supplied itself with food as well as a few of the county jails in this part of the state. I’m sure that wasn’t all they did. I know they also sold bread and other baked goods they made there.
In Georgia, there are factories and other shops inside the prisons. One makes eyeglasses for inmates statewide and another makes the mattresses that all prisons use. There is also a furniture making shop, but I forget where that is used.