I was driving in Italy recently on their Autostradas and I simply could not go 80 mph on those roads because they are narrower and more curvy that our interstates.
Well, you do not drive in the left lane, even if you are going 80 [130 kph]. Cars will come up going 100 mph and faster and you do not want to be there when they do. I relearned the importance of staying in the right lane unless I am passing.
Also, in Italy the car in the left lane puts his left turn signal on and leaves it on until he is back in the right lane. I thought that was a pretty good idea because it make you more apparent to the cars you are coming up on from behind.
Ever driven on a German autobahn? mmmmm...
We have the same exerience in the east of France around Mulhouse and north where our friends live. No one in the left lane unless passing.
I remember when I was a kid and folks used to flash their brights from behind you to alert you that they were going to pass.... maybe that was just in Texas, not sure.
Same in France and (if I remember correctly) Germany. It does make sense once you see it a few times... it seemed weird to me at first.