Ok, so if a man cheats on his wife and nobody finds out (sealed records), is he not a cheater then? Sorry, but our character and our actions define each other.
Yes, at the conclusion of the sentence the criminal will be released. Hopefully, by actually facing a consequence for their actions, they might decide stealing cars isn't worth the cost and they won't repeat the criminal activity. If they do, they will stay in jail longer. Some lessons require more teaching than others. 
But to be honest, I think you and I are going to have to agree to disagree because neither of us has a snowball's chance in hell of changing the other's mind.