The retribution vs, rehabilitation has fluctuated. There was some research in the '70s that showed that rehabilitation was not really impacting recidivism. Some said that research was flawed, for example because of the other things that were happening in that same period, much like after the Civil War had a similar effect. But a tough on crime mentality was embraced and now we have what we have. This is a decent overview with some good sources at the end:

http://www.pbs.org/moyers/journal/12282007/penalphilosophy.h...