He wrote them to teach his people how to live, how to act in every circumstance. For he wanted them to be understanding, just, and fair in everything they did. To learn, you must want to be taught. To refuse reproof is stupid. An unreliable messenger can cause a lot of trouble.
Reliable communication permits progress.
Everyone enjoys giving good advice, and how wonderful it is to be able to say the right thing at the right time. If you profit from constructive criticism, you will be elected to the wise men's hall of fame. But to reject criticism is to harm yourself and your own best interests. The Lord demands fairness in every business deal. He established this principle.