Well, think you're only seeing the most splashy uses. For instance, at high speeds, could use the thrusters to first, increase acceleration and speed, and second, have them also able to do a bit of thrust vectoring to help push the car's tires on to the pavement for better traction. And then on turns, have thrusters firing to help push the car into the turn.

Also, maybe the car is able to hover for short to medium distances, which for a military and offroad vehicles, could be very useful to cover all types of terrain