I used to think that way, but have more recently considered that the primary purpose of a justice system is to convince the populace that justice has been done, so they don't take it into their own hands, as this rapidly leads to escalations of violence and revenge. If all that mattered to the justice system were the perpetrators of crime then a reform based approach would be best, like you say. However I think really the main purpose of the justice system is to keep our animal behavior at bay. Even if we don't all like the outcome of every trial, at least we're not usually going after the criminals ourselves when dissatisfied with the penalty.Reform justice is the best model of justice and should form the basis of the penal system. Punitive and retributive justice are the result of animal instincts trying to foster prosocial behavior, but we can use our forebrains to devise better incentive schemes than "If a man steals, he shall have a hand cut off" or "If a man steals, he shall be flayed to death".
To change my mind, you would have to produce solid evidence that punitive or retributive justice schemes produce a healthier society were people are more prosocial, instead of creating a perverse incentive for antisocial behavior.
I don't have anything like the data needed to prove this idea though, so I don't think I'll change your mind here. Just saying I used to think very similarly, but I think at the time I wasn't looking at an important piece of the picture.