Oh, and remember that rubber tires and rubber-soled shoes provide virtually no protection from lightning. In fact, many victims of lightning strikes are farmers in open fields riding tractors with rubber tires.
It's the metal cage of the car that provides lighting a more conductive path around instead of through you.
That's different than laying in a ditch or sitting in a car. At least in the car, the body is higher off the ground, and a lower resistance path than you. Perhaps a convertible, open top, bare metal floor with a flat tire might be comparable.