Why doesn't a driver get motion sickness?

In more control. The driver of the car is generally less likely to have motion sickness because he not only has accurate sensory information from his senses (ears, eyes, touch) but also is controlling the car and can therefore anticipate accelerations, decelerations, and turns. This position enables him to calibrate his expectations of movement with the car's actual movement.
I wonder myself. Maybe because he/she is the only one in the car looking in a distance and anticipates turns?