Years ago at the Le Mans 24 hour race the cars were lined up on one side of the track facing out.   The engines were not running.   The drivers were lined up on the opposite side of the track.   When the gun sounded and the flag waved the drivers ran across the track jumped into their cars, started them and away they went.    Dr. Porsche figured out that if the driver could enter the car with the key in his left hand he could shift into gear with the right hand as he started the car with his left hand, thereby getting a bit of an edge right at the beginning of the race.    Maybe a 3 to 5 second head start.
So now the fob or key is always on the left as "Tradition".     More than you wanted to know.   

Ron