IIRC, Prouty had a discussion of this in his column in Rotor & Wing some time back.
As for the main rotor, it seems to be just tradition. Sikorsky, in the very early models, had some one way & some the other, depending I surmise on the simplest engineering on that model. Having flown both, I can say it's a pain to switch from one to the other. Hovering is no problem, but when you turn final, drop the power to descend while rolling into a turn, & automatically push the wrong pedal, everyone aboard knows it.
