One simple thing is that you drive in the left lane, so when you want to turn left, you don't have to cross oncoming traffic. More than anything, it's just an historical thing. That's the way it has always been done in those countries. What I meant by it makes sense, is that it is virtually no different than driving in the right lane. So, once you drive in the left lane for awhile, it makes just as much sense as driving in the right lane.