BC,
Very historical, going back to the Sikorsky R-4 during WW2. First two seat helicopter. It only had one collective (the thingy on the left of the seat that makes the world get smaller if you pull up on it) it was in the middle between the pilots.
Most of the new trainees flew from the right side as the old hands all took the left. In time there were more "right seat pilots" than lefties so things got standardized that way.
In fact in those days there were "right seat" pilots and "left seat" pilots. The difference was so great because to change ment completely changing your hand positions, not as easy to do in a helicopter as in an airplane. I've tried it in a Bell 206 flying in the left seat using my right hand for the collective left on the cyclic. Nearly crashed many times while trying to hover. No dought you can learn it but it really messes with your mind.
Also the practical reason is, in the right seat you have your left hand fee to tune radios, etc. (You can friction the collective and let it go) In a helicopter, other than one with SASS or AP, you cannot let go of the cyclic in your right hand. Helicopter wants to flop over and kill you if you do. In fact if you must let it go, fold a map etc you learn to hold the cyclic between your knees and rock your ass around in the seat to keep the dirty side down. Great way to scratch an itchy ass at the same time.
Gets interesting in alot of the small, Bell 47 Hughes 300 and 500, helicopters as the pilot is on the left side, to make more room for pax on the bench beside him, you are constantly changing hands in cruise to hold the cyclic with your left hand to use your right to tune radios, adjust the carb heat, or cabin heat. Takes a little time to get used to the change of hands. Also takes time to learn to get all the bits done before you are on final because there is in addition to the "landing decision" point a "no hands change now" decision point.
So if you want an adventure go take a helicopter lesson some time, its the greatest flying machine of all. You will say its "impossible to fly" when you start but in time you catch on. All the airplane pilots I've given joy rides to end up dropping out of the airplane game to master the slingerwinger full time.
I'm still mastering the beast after 14000 hours, thought I knew it all when I had 10000. I've had 4000 more to teach me I had more to learn.
Keep your turns up, lest the earth arise to smite you.