What happens when they sell the car in a country that drives on the other side of the road? They would have to move everything around.
They don’t. It stays on the same side as it was. They don’t move the bonnet opening lever or the indicator stalk either.
They could design the fuel tank to be symmetrical about the axis parallel to the car’s axels. This would let it be flipped during installation at the factory to have the refueling port facing either side. Then the only difference would be the body panel and little door that covers the gas cap.