In the Bible a primary image of leadership is shepherding. Jesus called himself the Good Shepherd. The image of a shepherd is pretty common in the Bible. The analogies are simple: God's people are like a flock of sheep. They can be attacked, stolen away, wander off, and, left on their own, find themselves without protection, food, and water.
Why would Jesus teach the people God's ways? Jesus could have given the people many things…but he gave them his teaching. Teaching God's ways provides what a shepherd needs to provide for the flock: protection, guidance, direction, sustenance.