You're simplifying the opposing position in a way that isn't fully honest. There are at least four purposes incarceration can serve: rehabilitation, retribution

You're simplifying the opposing position in a way that isn't fully honest. There are at least four purposes incarceration can serve: rehabilitation, retribution, dissuasion, and separation. Rehabilitation meaning, giving people the tools and resources to avoid recidivism. Retribution being, punishment or justice for the benefit of the victim. Separation being physical removal of people incompatible or dangerous to society. Dissuasion being what you describe, punishment that rational actors will take into account when deciding to take an action. Pro-rehabilitation people argue that rehabilitation should be the first priority, and retribution the last, with separation there when necessary (think: life sentences for people who murder without remorse) and dissuasion somewhere in the middle. Compare prison to something like an inpatient addiction recovery center, which aims to rehabilitate and separate (although sort of in the reverse way) and how much more constructive that is. I don't think there's very many people at all (even among like hardcore prison abolitionists) who believe that it's possible to entirely do away with some form of separation of people who are dangerously incompatible with the norms of society. If nothing else, mentally ill people who can exhibit violent behaviors will continue to exist. All that said, your comment also has very little to do with murder rates. Those don't really correlate a lot with petty crime or even petty violent crime. Someone who makes a living breaking into cars doesn't suddenly jump to murder.