According to Evans-Pritchard, Azande commoners did not accuse chiefs of witchcraft because witches bewitch people they envy, and chiefs do not envy commoners.
There was no reason for chiefs to envy commoners and be jealous of what they have, because usually they had much more than the commoners. There wasn't much for them to envy, and thus to turn to witchcraft, according to the commoners in these tribes.