In the US, at least, they milk the prisoner's families every way they can. Charges for phone calls, web-to-paper letters, commissary items, and so forth. They also withhold basic necessities like soap, toilet paper, toothpaste, etc, to drive up sales. And, policies like 2 meals a day (instead of 3) on weekends. They even take the first $100 of your prison account for health care charges. It's an embarrassment for a first world country.
Combined with the now ubiquitous cheap online background checks, one felony is enough to ruin your life forever. You end up being dependant on family members for life. The justice system in the US is built around some Puritan idea of punishment, with no notion of rehabilitation.
Source: Am one of those family members supporting a felon.