I had the misfortune of having a wannabe-politician as prosecutor going after me. She didn't care that I was a first time offender, and she could care less about the destruction to my profession and my ability to support my family. I was lucky enough to have a judge who had the sense to realize what was going on, and a lawyer who, due to the simplicity of the case, didn't bankrupt me. I'll never forget looking into the prosecutors eyes as she treated me like anything but a human being, and tried to needlessly destroy my life. Had she succeeded in her stated goals, I would have lost my job at a time when I couldn't possibly afford to. My consequences for my infant son and stay-at-home wife gave her zero pause, but thankfully the judge saw me as a human being, and was intelligent enough to conduct an instant cost/benefit analysis for society in her head.

I seriously doubt that any of this is unique to a few prosecutors. At the end of the day, their incentives are not for the social good. Individually, they want a flawless record as a victor, costs to their victims be damned.