Good question, interesting answer! First, a six-sided pencil is more compact to stack than a round barrel, allowing more pencils per inch to fit into a box for shipping or storing. Second, some find that the angles of a hexagon-shape barrel make it easier to grip. Lastly, a custom pencil with a hexagon-shape barrel offers fewer imprint options due to the limited height of each of the separate panels. A round barrel can usually accommodate a range of imprints including text, a logo, or another image.