The inclined angle is use to control the change of the caster angle when off power. When off power, the weight will transfer to the front of the car and compress the front suspension. The upper wishbone will move upward that means the pivot point will move forward ( due to inclined angle of the upper wishbone rotating axis ). When the upper pivot point move forward means the caster reduced. Smaller caster will improve the steering when off power. Larger inclined angle means larger change in caster angle.