This allows divine justice to work. We are compensated through the acquisition of knowledge that brings responsibility and faith. By furthering spiritual truths, we are be able to express ourselves in ways that would not otherwise be possible. Whatever good you do, you are the better for it.
Retribution is similar to the Law of Karma and opposite to the law of compensation. Causing harm to one's life or to another would invoke this law. For example, whatever selfishness you show, you are the worse for it. Without this law, the sinner could have spiritual equality with the saint. If by repenting, a person could rid themselves of sins committed, it would create a mockery and a travesty of this law.