Fashion made Bell change to the right
More like "practicality".
You need to hold the cyclic all the time, either in the hand or between the legs. You can let the collective go for short times, using collective friction or lean the left leg against it. To change radios or adjust QNH you keep flying with right hand and use left hand to make the adjustments. Thus, easier to have pilot on right, with collective between seats.
For a machine with a front bench seat, the lever needs to be on the left of the seat, so the left-seat pilot has to juggle hands to play with radios. In the 47s and bench-seat Squirrels, the engineers take out the bench and put in single seats and a set of dual controls for a dual check or endorsement.