Because incarceration is penitentiary, which means criminals are made to pay for their crimes - not to be rehabilitated. There other countries where incarceration works, for example Norway [1] - primary because they focus in rehabilitation. Incarceration is not the problem, the typical opinion of the purpose of incarceration is (justice through revenge).
Incarceration is 100% effective for what America wants it to achieve: penance.
Incarceration is 100% effective for what America wants it to achieve: penance.
[1]: https://m.phys.org/news/2016-08-norwegian-prisons-criminal.h...