Charles Ellicott Commentary Exodus 18:1

"Now Jethro, the priest of Midian, Moses` father-in-law, heard of all that God had done for Moses, and for Israel his people, how that Jehovah had brought Israel out of Egypt." — Exodus 18:1 (ASV)

The people want decisions which they can feel to have Divine sanction—they “come to him to enquire of God”—and the ruling of inferior judges would not be regarded by them as equally authoritative.