As Australia drives on the opposite side to the USA - the general thing to do is slow cars move to the left and most overtaking is done in the "fast" / right lane(s).
In practise though, people go slow in the right lanes and are not considerate of other drives. Some even think they have the right to prevent others from speeding and deliberately do 5-10km/h under the limit.
The thing is, by not following the practise you cause other impatient drives (rightly or wrongly) to weave in and out of lanes passing on both sides which increases chances of an accident - due to the increase number of lane changes.
In states where it's legal to overtake on the left, there's no cultural obligation to stay in the leftmost unoccupied lane unless overtaking, and so cars end up scattered all over the lanes. Add in the government's myopic 30-year fixation on speed limits as the answer to any and all road trauma statistics (and their huge expenditure on propaganda to convince the general public) and you get self-righteous idiots doing 10-20km/h under the limit in the rightmost lanes smugly convincing themselves that they're "making the road safer" as road trains try weave around them.
