Exactly. Taking away someone's liberty is a substantial punishment, and the imposition of longer sentences for more serious crimes should slake the natural des

Exactly. Taking away someone's liberty is a substantial punishment, and the imposition of longer sentences for more serious crimes should slake the natural desire for vengeance to some degree. But the victim is not the only stakeholder in the justice system. There are also the accused (prisoner's rights), and society at large (lower recidivism). The interests of all need to be balanced.