I love that verbiage, because IMO it really gets to the crux of the issue: many drivers think that if they're going the speed limit, it's OK to park out in the left lane.

The problem with that is nearly everywhere in the US the average rate of speed on highways is about 5 miles over the speed limit, so if you're doing the limit you are going to be one of the slower cars driving.

It really is about cars passing you. If you're not passing you need to move over.