Even without thinking too hard about purpose prisons actually serve in society, it's self-evident to me that prisoners and their families should not be thought

Even without thinking too hard about purpose prisons actually serve in society, it's self-evident to me that prisoners and their families should not be thought of as piggybanks from which value should be extracted. This creates a perverse incentive to keep more people in prison, which is exactly the opposite of what we (as a society) ostensibly want.