Mmmm....
I have wasted years in various bars discussing this with many aviation type drunks ... ooh I mean pilots ...
After sufficient liquid logic was applied to the subject it seemed to be decided that the reason (originally) the command position was on the left side of the cockpit was because of provisions in those very famous "Rules of the Air".
When overtaking, passing slower aircraft (Zepplins etc) trying to avoid a head on collision etc etc etc safe manouvering required alteration of heading to the RIGHT .... therefore in order to continue to keep the other aircraft in safe sight the best place for ones bum was to be on the left hand side of the aircraft.
Of course as all rules were meant to be broken .... so various helicopter manufactures have over time decided that due to the inconvenience of the classic controls set out it was necessary to put the helicopter captain on the RH seat for ease of "knob twiddleing" whilst also trying to keep the silly machine the right way up!
Howzat sound???