One which hasn't been mentioned and is not the original reason but is very valid is seaborne helos landing on a carrier deck can not land from the right side of the ship as there's some large lumps of steel in the way known as the 'island'. So landing from the left of the ship a right hand seat gives you a much better view (Try cross cockpit deck landing at night for a bit of a lark!!!)
Oh and flying right hand on collective's a real sod if you'r not doing it constantly. Just think in the hover drifting forwards normal correction right hand back ...ops the sods climbing so left hand goes down....bu??@^ it's going faster etc. etc. Tried it years ago on Gazelle, simple corrections ok, but ask me my name and it went to a ball of chalk so fast it was not funny.
