Because prayer is so important to God He even accepts prayers from intercessors that do intervention on behalf of others. They are God's effective secret agents with an all time "wireless" connection to Heaven. They do His bidding and release His will into the lives of many.
"So I sought for a man
among them who would make a wall, and stand in the gap before Me on
behalf of the land, that I should not destroy it; but I found no on" (Ezekiel 22:30 NKJV).