It may be accurate in some cases. But many criminals commit their crimes knowing full well what they are doing, and with no regard for those who are hurt by their actions, and show little or no remorse (unless they think pretending can reduce their sentence).
Now, many are in prison due to unjust laws, selective enforcement, or a flawed prosecution incarcerating the wrong person. But let's not lump those problems together with those who intentionally harm others without remorse.
I think many of us are aware that felons loose their right to vote. I guess I assumed you would be blocked from voting. So I never thought about what the penalty should be. Now that I’ve seen the penalty, I’m appalled.
Frankly, I think we should quit criminalizing everything. The governments responsible for jailing criminals, no-fly lists and a lot of other things. Why not take responsibility for blocking felons from voting?
If that's what the voting public thinks it's for, then for all practical purposes, that's sure as hell what it's actually for.
In other words the rehabilitation occurred during and as a result of the criminal act.
Except the sociopath angle - a person who commits crime for fun is quite likely to find another fun crime to commit.
Punishment has three purposes: retribution, rehabilitation, and deterrence. We seem to be suffering from a contemporary bias against retribution [0]. However, these three purposes are intimately connected. When a punishment fits the crime, we communicate the severity of the crime to the criminal. In that way, we help facilitate rehabilitation by making it clear how grave his offense has been. Deterrence is facilitated by the same token. Obviously, these are not absolute measures. For example, a criminal may be unrepentant, but then rehabilitation is not possible. In any case, adequate remorse does not remove the possibility of retribution (though a sincerely remorseful criminal would accept that he deserves commensurate punishment), but it does allow for mercy.
[0] A common confusion here is that retribution entails hatred of the punished. It does not.
And even if they do rehabilitate, our society is not properly set up to help them come back, so the retribution often outweighs the crime. They do their time in prison- but essentially they do time the rest of their life, because when they come back, they aren't treated as if their retribution is complete.