It can only be because you want the absolute maximum strength above all other considerations. The bogie options of 26 and 30 tonnes will give generous margins of capacity to meet all requirements.

Both share the same basic design. There is a central mounting point midway between the driving axles, to give as much articulation and traction as possible. Torque rods link the frame to the axles, which isolates the springs from driving and braking forces in order to give better protection to the chassis from road shocks.