The hexagon part has the angle 15° symmetrically, so it can work with the same level (rotating with the swing angle 30°)as the dodecagonal box end wrench.
Removing the edge rounding of the hexagonal opening part, the contact area between the opening area and a bolt/nut is larger.
The handle part has 45° x 10° of the rising angle and the easy-to-hold shape that a power is easily put, which fits hands.