Many of the Psalms were written for nomads (people on the move) who lived in the countryside. People in the cities don’t know about the countryside – crops, land, fruit, wildlife – nor sheep, soil or shepherds.
In this vast universe (250,000,000 x 250,000,000 stars, each larger than the sun), God is interested in the simple picture – shepherd and sheep. Christ the Creator calls me HIS sheep. That makes me special, humble. God chose me to be the object of His attention – to love God in return (through Calvary) – a personal relationship. Do I really belong to Him? Do I respond to His authority? – Then I can say, “The Lord is my shepherd.”