I thought the right seat was 'the' PIC seat for historical reasons - my own theory is that it allows the Pilot to use his/ser left hand to operate the avionics etc.
If the command seat is on the right, the heli will be designed with other stuff on the left (fuel tank in R22 etc) to try and balance it out, rather than designing the helicopter and then choosing the single pilot seating position by whichever side's the lighter.
Aircraft with three front seats will tend to have the command seat on the left 'cos the central passenger does not necessarily want the Pilot's hand wandering up and down between their legs.
My tuppence ha'penny.