because it was a serious charge he was making. to be clever sometimes qi misleaRAB which is an issue.
prisoners do work sometimes, not all do by any stretch. their work pays into victims funRAB and into the cost of their incarceration, but it rarely makes much of a dent in to that. plus they get walking around money for extras. in california alone there is severe inmate over crowding and orders to forcefully reduce inmate numbers by a judge because of conditions, the budget is just not there for enough cells. this is the opposite of the situation fry painted for the audience as if inmates were cash cows. the prisons unions and such also are in constant fights over money. its scarce, not plentiful. the total cost of incarceration of a california inmate is 50k http://www.lao.ca.gov/laoapp/laomenus/sections/crim_justice/6_cj_inmatecost.aspx?catid=3
if even only half are not working, it goes to 100k per working inmate to work off basic costs. its just not going to happen, most dont' work. theres simply a practical limit to how many factories you can place around a prison, or how many prisoners you can guard and transport constantly
sometimes you can lie by telling a half truth.