The fire and brimstone crowd did not initially lock people away for extended periods of time. They whipped people, publicly shamed them, executed them, etc. T

The fire and brimstone crowd did not initially lock people away for extended periods of time. They whipped people, publicly shamed them, executed them, etc. The "penitentiary" was explicitly a reformist idea that people could be improved by education instead of punishment. Instead of whipping and executing criminals, we would put them in an institution of "penitence" -- quiet reflection leading to appreciation of the wrongness of one's actions and the need to act in harmony with the benefit of others and society as a whole. This enlightened, benevolent approach would stress mutual benefit rather than punishment, even if it wasn't pleasant to lose one's freedom temporarily. After a while we lost our optimism about the penitentiary concept and decided that being locked up was just a pointless ordeal, which made it popular with people who believe the goals of criminal sentencing should be punishment, deterrence, and keeping dangerous people separated from society, and less popular with those who favor a benevolent approach.