The whole point of a legal system is to ensure that individuals who break or abuse the law are punished, allegedly. Of course, the system is flawed, with many innocent people ending up in prison, and many criminals ending up in government—but I digress.
The point is that "criminals" in modern society are, at least in theory, and depending on the severity of the crime, given a chance to rehabilitate themselves. And many, many convicts serve time, leave the system and go on to become upstanding members of society—which is more than you can say for most people, who break the law (you've probably already broken one today!) and never do time.