Tick, tock

On which arm do you wear your wristwatch?  Chances are that it's the left - but why?  I've been thinking about this, and I reckon it goes back to the days before battery-operated watches, when you had to wind them up.  Worn on the left wrist, the winder would be readily available, whereas on the right wrist it would be on the "wrong" side and winding would be awkward.