Honestly, I'm divided on this. Sounds right that prisoners should work to cover the costs of their incarceration. However.. there's the competition angle Fletch mentioned, and there's this incentive to make the whole thing a huge business:...get out of doing hard honest work...
first you have companies renting out cheap prison labor.
then you have companies writing laws that will make more prisoners.
They talk how positive this was going to be for the community, the amount of money that we would realize from each prisoner on a daily rate.