Pilot on left/right
I flew Bell 47G in training with the AAC in 1965. The Bell 47 was one of the first successful main stream helicopters produced after the war and I've always understood that, because thats where fixed-wing pilots traditionally flew from, there was no reason to change it.
When Sikorsky began to produce helicopters they were used mainly for ship-board operations which must have been one of the biggest steps forward in making people aware of helicopter capabilities and potential. One of Sikorsky's first was the S55 with provision for two pilots. As the island on a carrier is to starboard, it made sense to have the pilot sitting on the right to give the best view of the flight-deck on approach from the port side.
All the helicopters I flew after the Bell 47, from the Saunders Roe Skeeter up to the commercial Chinook, were designed to be flown or at least commanded from the right-hand seat withe the exception of check rides where the TRE/IRE commanded from the left.