The purpose of the legal system is NOT to offer retribution to victims. Making the murderer suffer won't bring back your kids. It will accomplish exactly nothing, in fact.
Actually that absolutely is one of the stated purposed of state justice. This also has the benefit of preventing private vendettas, if the victims feel the criminal has been punished enough.
In Europe, that is not true. The stated purpose of the justice system is that of deterrence. Exerting justice for the reason of revenge is nothing more than catering to the lower instincts of people and that is very much at odds with a civilized society. If you really believe that people are locked up so that the victims feel better, you have watched too many bad American TV dramas.
Well, it is widely documented in introductory criminal law courses as a part of the three Rs (removal, retribution, retaliation) or in more accessible material such as
Accomplish something? Oh yes it does! It served to attenuate the absolute day by day anguish of living with the fact that the murderer who blotted out the existence of the person you knew is set to enjoy a new life out of prison while their victim continues to rot. It also solves the potential for recidivism.
It won't accomplish anything for the victims' relatives, that's true. But other people will feel safer knowing that at least some percentage of children murderers are locked out for good.
It's not about making the murderer suffer either, it's about preventing future crimes. When you have cancer, you don't kill cancer cells because you want them to suffer. You kill them to prevent them from killing you.
If harsher penalties were the solution to preventing serious crimes, you'd think the death penalty would have fixed that, right?
Turns out the only thing harsher penalties do (beyond a certain threshold) is make it more likely for crimes to escalate because there's no point restraining yourself (if it means leaving witnesses) if you're already going away for life / going to be murdered by the state anyway.
As a matter of fact, the best way to prevent crimes is actually preventing crimes. Figure out why people commit crimes, then try to fix that. E.g. if you stop treating addicts as criminals you can solve their underlying psychological/social problems and they don't end up robbing people to pay for drugs.
Problem is, there always will be murderers, abusers and thieves. Preventing crime is the right thing to do, but I don't think it is the answer for determining right degree of punishment if a crime is committed.
Okay, consider this: you're talking about punishment.
What, exactly, is the point of punishment?
Are you trying to prevent future crimes? Great, we're actually talking about crime prevention and severity of punishment is a red herring (because we actually need to consider punishment as merely one option among many).
Are you trying to satisfy victims? Okay, but now you're saying the punishment basically serves as a synthesised substitute for mob justice -- so why pretend there's anything humane about it at all?
Are you trying to deter other would-be criminals from doing the same? Great, we can actually measure the effectiveness of that empirically (spoiler: it's not great) and adjust punishments accordingly.
Or we can just build more prisons and put more people in jail (or murder them if we really don't like them) because that has worked out so well in the US.