Au contraire. While things might well be different on the other side of the pond, when my parents were in HMP Shotts (for work, not at her majesty's pleasure) one of the guards explained that prisoners wanted to work, and not allowing a prisoner to do so was one of their most effective sanctions. The reason's simple: if you're not working, there's fuck all to do in prison; it's boring staring at your cell wall all day.
Again, while things might be different in the 'States, the prisoners at Shotts were paid for their work (making roadsigns, incidentally). Nowhere near a living wage (after all, they're getting bed and board provided), but some "pocket money" that went into an account that could be redeemed at the prison shop, mainly for things like more luxurious toiletries.