Those are state by state decisions. Many states choose to fund the prisons by taxing phone conversations. None of it is encouraged by the private industry - the prisons have a contest between the main vendors (GTL and Securus) and whoever offers to pay the highest percentage and amount of revenue wins. They of course know who is going to pay, but the public has a hard time associating “let’s raise taxes and spend more on prisons” with a reduction in telecom cost for the prisoners. And even those who do get it, view it as yet another way to be tough on crime. Ironically, having frequent contact with family is the best way to reduce recidivism.