[Nasrudith]

Payment for labor is important on pragmatic grounds alone given incentives. If given only negative enforcement then it is do enough to avoid it and more paid overseers. If there is some positive enforcement then incentives align enough to not just "pretend to work whenever they can get away with it" as optimal.

Not to mention the rehabilitative effects - you want convicts looking for delayed gratification and honest work instead of big scores.

[jpindar]

Also, giving prisoners privileges such as television or the chance to earn a little money makes it easier to prevent misbehavior by threatening to remove those privileges. This has been shown to be as effective (in most cases) as harsher punishment, but without making the prisoners as angry and resentful.