When backing up a commercial vehicle, why is it highly recommended to back from the driver's side (left side) rather than the passenger's side?

1. Because the driver has a much clearer view of the rear and side of the vehicle from the left mirror and window
2. Because vehicles are mechanically designed to turn sharper to the left
3. Because backing to the right is prohibited by municipal bylaws in Alberta
4. Because backing to the left requires fewer steering inputs