Thanks all
The consensus seems to be that it just worked out that way, so I'm going to file this alongside "right-hand/left-hand traffic" and "first floor/ground floor" in my head--just one of those differences that make international travel interesting.

(Fun fact that is not related to anything: the only place under US jurisdiction that drives on the left is the US Virgin Islands. Of course, they get most of their cars from here, so their steering wheels are all on the wrong side. There might be a business opportunity here for an enterprising resident of a left-hand-traffic country, but I haven't run the numbers on it.)
(tellum0 is spelled with an 'o', Sat 27 Feb 2010, 5:54, Reply)