Nothing focuses the mind like the prospect of being shot in the morning. Death is a blessing because it forces us to distinguish between the lasting and meaningful and the trivial and fleeting. Death wasn't part of the original plan, but after Adam and Eve ate from the Tree of Knowledge, G-d decided man needs the discipline of a final exam. Cain's evasion of responsibility for killing Abel. He implied the guilt was actually G-d's for failing to prevent the murder from taking place.
Punishment is only just when it's commensurate with the crime.
In actual practice, Biblical courts didn't remove eyes or teeth, but calculated their monetary value and assigned that amount as damages. This is the Torah portion containing the giving of the Ten Commandments. The portion concludes with the Almighty telling Moses to instruct the Jewish people not to make any images of G-d. A person who keeps all of his money for himself in contradiction to the Torah's command to give charity shows that his faith rests with his money and not with G-d.