I mean mass incarceration for "long haul" (lets says 30+ years) prison terms absolutely could be argued to "improve" society by removing people who have broken the social contract.
The classic problem with prison is short and frequent sentences that fuck someones life up just enough to prevent them from being a "good" member of society but not long enough to really keep them away from the general population.
Who exactly considers that the "classic problem" of prison? Your reasoning strikes me as perverse. This "social contract" is the rule of a few elites with racially charged political agendas over the many, look into the history of drug laws. It's not a just contract if you are manipulated with false propaganda and coerced by force into signing.
> "social contract" is the rule of a few elites with racially charged political agendas over the many, look into the history of drug laws
There are a lot of violent crimes with shockingly short terms. Including for repeat offenders. This isn't a problem for elites, who can afford to stay away from these problems. It's a problem for common, law-abiding, unexemplary Americans.