Neither. They are for sequestration. They are a place to put people that society just doesn't want to deal with. Punishment is just a side-effect. This is the reason we put people awaiting trial in the same facilities as people who have been convicted of crimes.
Rehabilitation is not even on the radar.
So, given that the pragmatic benefit of incarceration is protecting the innocent from being victimized, which presumably we all support, we should look if there are other less crude ways to achieve the same goal. I understand that Drug Court and similar programs have had some measurable success. But we can't forget there are very bad people who will treat diversion programs as a joke and an opportunity to continue to prey on others. Those individuals should be incarcerated, not to punish, but to prevent them from offending again. Rehabilitation would be wonderful and the opportunity should be offered, but some persons just don't want to be rehabilitated.
This is not the purpose of incarceration in Germany or the Scandinavian countries. The purpose there is simply loss of freedom for a short while as punishment, and assistance to better yourself for when you're released.
And their low recidivism rates bear this out.
But hey, at least it feels good to some people on a visceral level! Those world-leading incarceration rates won't maintain themselves, you know.
As a non-American, I'll never understand the cultural cognitive dissonance in simultaneously trusting the government to be "tough on crime" - despite all evidence that this approach backfires strongly - and distrusting their intervention in just about anything else.
[1] https://en.wikipedia.org/wiki/Incarceration_in_the_United_St...
Not defending the medieval “justice” system in the us, just being clear.
Additionally, a lot of times it makes sense for someone awaiting trial to push the date back as far as possible, in the hopes that witnesses or the prosecution decide not to show at trial or forget the offense. Maybe you can then get off with time served and without a conviction.
Which means jails are "how long can you survive in the worst possible place so your life is not ruined more than it already is". Because America is a fucking shitshow and we just don't give two tugs of a dead dogs dick about basic human rights.
I really hate this country.
This was a major factor of the Ferguson riots which quickly fell out of the simplistic press narrative. The mayor decided to lower taxes and fill the gap by charging people who were arrested. The consequences of that are no surprise.
(Not sure why my GP comment was downvoted. They are different systems with different pathologies).