The difference is, there is a lot of money to be made by private prisons using a captive workforce that are paid pennies. Corporations need to expand their bottom line year in year out. What limits private prisons is the number of inmates. If they can get more inmates, build more jails & farm out more cheap labor to other corporations for a fee, they are set to make a killing. If they could get their hands on a privatized police force to feed them more slaves, they would jump at the chance. Nothing would stop them from buying local councils, so that their corporation would be awarded the contract.