I don't know if I buy that prosecutors throw *everything* they can at you. I was charged with shoplifting once, and I didn't even get a public defender. Instead had to argue my case with the prosecutor directly, and she herself filed a motion to dismiss, which the judge approved. She said her goal was justice.
Just prior to that (I had to sit in the court room and watch her and other prosecutors argue their case against other defendants until it was my turn) I watched her tell the judge that she wasn't offering any kind of plea deal against the previous defendant and that she wanted to go to trial with him, which I'm guessing in his case she had some pretty clear cut evidence for conviction.
(I went home very relieved that day as I had just gotten done watching the BOOK getting THROWN at people by the judge for similar crimes just prior to the judge smiling at me and telling me my case had been dismissed and I may leave.)
I have been arrested mainly times in my life. I was a no good junkie who supported my habit by shoplifting. During my stupid 15 year drug addiction, I've gotten in to a lot of scrapes legally, some of which I wasn't guilty of, just at the wrong place at the wrong time. Most the shit I was guilty of.
The problem? Because I could no afford to pay bail, or get a decent lawyer, I was always stuck with public defenders. During probably 20 court trials, I have had only 1 good public defender that actually tried to get shit done, rest the time, they didn't give a fuck. And because I didn't want to stay in jail till trial (which would of been at least 6 months of jail time), I'd take guilty pleas so I'd end up staying in jail a week or so.
TL;DR I did bad shit, I went to jail for it. Because I was poor and couldn't ever bail out, I would of spent years in jail waiting on trials for crimes that don't ever carry more then a month in jail. So I plea bargained because otherwise I'd spend more time in jail trying to prove my freedom, then actually taking the guilty plea and time served.
Fucked up system.