1 Samuel 8:5

and said unto him, Behold, thou art old, and thy sons walk not in thy ways, his advancing age was robbing him of the vigor and energy needed in the government of the nation, and the misgovernment of his sons resulted in a general degeneration of all authority; now make us a king to judge us like all the nations. All the heathen nations round about had kings to rule over them, and this the petition of the elders, which undoubtedly had in mind Deuteronomy 17:14, emphasized, especially since Moses virtually had such a contingency in view.