Its a hard problem. If the goal of prison is for people to be able to be a non-destructive part of society when they get out, they need to learn skills and be

Its a hard problem. If the goal of prison is for people to be able to be a non-destructive part of society when they get out, they need to learn skills and be employable. That cannot be done if they are kept from working and earning. However, if they earn money, that is obviously something of value, and can be traded or used against them.