Most piano methods begin by teaching the student how to read music. While it is important for all students to be able to read music, this often delays the begin of lessons for young children who do not yet know how to read. Beginning with reading also tends to distract students from learning proper technique by directing their eyes away from their hands.
That is why the Suzuki Method begins each student with ear training. The first songs a student learns are learned by ear, enabling both student and teacher to focus on developing the student's technique, so that when he does begin reading, his technique will be solid enough not to deteriorate when the eyes are directed up at the musical score.