It would help the nation to improve the economy.
It prevented slaves from learning how to read and write. It also made it scary for them to escape because they allowed slave owners to whip them or hang them for trying to escape or committing small or big crimes.
When considering Job's friend's approach, first, one must take into account Job's current situation. He had lost all of his sons, his wealth, his health, and probably the respect of others around him and his friends did little or nothing to ease his pain. For example, when trying to comfort him, Bildad, said that if Job's son died, its because they were sinners or evil men and they deserved to die. Eliphaz hinted that Job was not a righteous man, and he was being punished by God, who doesn't value the good actions of his servants.
When reading their full speech, one can see how they not only failed to ease Job's suffering, but also contributed to increase it. Blaming him from his suffering, blaming god, or insinuating that god was cruel. A god that Job deeply believed in. If one could say that they did at least something right is that they stopped Job from feeling sorry of himself. And when the last of his friends Elihu stepped in he helped him to see the bigger picture. And how he could still be a good man, and be suffering, because he was not perfect, and he could make mistakes.
A better approach could have been starting with kind words, feeling truly sorry for his loss, helping him to see that his sons had no blame in what happened, and that god could still be there to support him. And when the time was right, help him to stop feeling sorry of himself, in a kind but strong way, as Elihu did.
