What is the significance of carrying a casket on shoulders?

The ceremonial function of pallbearers dates back to ancient Rome. The person's cloak or garment was referred to as his pallium. It was spread over the body or coffin from home to the cemetery. The pallium was carried by a friend or a loved one, while another group of men carried the body mounted on their shoulders.
By the Middle Ages, the pallium simply became the pall, a rectangular cloth that typically covers the coffin while lying in state at a Christian Church. One group of men were assigned to carry the coffin, while another were charged to proceed along side them to make sure that the pall did not drag to the ground.
A pall-bearer in the USA will carry a casket by the handle around waist height. In the United Kingdom and Ireland, the casket is carried on the shoulders as the handles are for the most part decorative