I have read that because of torque, helicopters (or at least American designed helicopters) like to turn to the right, so right turns were often performed.

So for visibility, the aircraft commander sat on the right.

The comment about cargo doors being in the right (like the S-55 and S-58 variants) would substantiate this, but instead of the pilot being put on the side of the door, the door was put on the side of the pilot.

But that does not explain why the Bell 47 and Hiller 12 series, the most common helicopters of their generation, had the pilots sit on the left…until you recall that they had a wide bench seat for two-three occupants. Putting the pilot in the far left made room for the collective.

However, Many modern light helicopter types keep the pilot on the left….The EC130 I inspected last week seemed to be set up for a left pilot…it has three bucket seats in front of its wide cabin.