This is probably because a driver has to use his hands to handle the steering wheel, change the gears or operate other mechanicals while driving the car. A higher armrest can be a barrier to the free movement of the driver’s arms. With a lower armrest, the driver will be comfortable operating the car and taking any measures or moving around in case of an emergency. Likewise, a higher armrest will make the driver uncomfortable in the seat and can lead to any difficult situation while driving.