Sascha
The answer is little known and very simple.
As the multiplier GENERALLY has a rubbish retrieve rate the handle was put on the right, most peoples stronger side, rather than the left, some bright spark worked out that you wind 3 times faster with your dominant hand and arm. It's all a hang-over from the 'pre fixed spool' centerpin and single action flyreel days of long ago.
Also precise drag control, whether via rim or star, comes more naturally with the dominant hand.
regards
Jeremy Airey