I think there is some sort of relationship between it and the English driving on the left side of the road? Just saying, please , no offense to anyone.
Dean, Smith & Grace were known of manufacturing some nice cutting lathes in their time and still do if you can afford to buy one. And on most of their lathes, the carriage handwheel is on the right side. Not sure about the operation of the half nuts and the cross slide and carriage handwheel, sounds confusing to me. My brothers have operated them back in their machining careers and swear by them!
It is my understanding that back in the old days when men fought with swords from horseback, that it was customary to ride on the left side of the road, path track. This made it easier, as most men were right handed, to wield ones sword against an oncoming opponent.
Somewhere down the track, after the American war of independence, American teamsters decided to change to right side of the road, probably in an effort to throw off any ideas that were British. and probably because they were friends with the French at that time, the French picked up the idea. The as Napoleon started conquering parts of Europe he made it compulsory to drive on teh right, and thus it spread.
However today, most countries that were former colonies of Britain still drive on the left. The odd one out is Japan, never a colony, but for their own reasons continue to drive on the left
The result is some 35% drive on the left and 65% on the right.
By the way the Dean Smith and Grace lathes are somewhat legendary. During may apprenticeship years there were a few around my home town Adelaide, and although I never had the privilege. a couple of the guys I knew in trade school, had them in the factories they worked in. Rumor had it, that a good operator could reliably turn to 1/10th of a thou. that is 0.0001" Pretty impressive.