Ya know, it really IS more of a question of why do fixed wing drivers sit on the left in my mind...in single seat airplanes (tactical jets and military training aircraft) the stick is handled in the right hand and the throttles handled with the left hand (so, similar to how right seat captains handle controls in a helicopter)...why multi crew airplanes put the captain in the left seat is anyones guess.
Just my two cents worth.
HP