I assume you’re not being intentionally dishonest, but have instead been taken in by propaganda, so allow me to remind you that the primary purpose and effect of incarceration is preventing reoffending. Fortunately a tiny minority commits the vast majority of violent crimes[1], so considerable reduction can be achieved by containing those criminals’ ability to commit crimes.
[1] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3969807/