This is because Shotoku Taishi was worshipped as a guardian deity of construction and woodworking based on the belief that Shotoku Taishi was engaged in large scale construction projects including Shitenno-ji Temple and Horyu-ji Temple, and defined various vocations.
これは、四天王寺や法隆寺などの巨大建築に太子が関わり聖徳太子諸職を定めたたという説から、建築、木工の守護神として崇拝されたことが発端である。