It is amazing the number of people that do not understand the road rules.
As a side comment, in Germany when I lived there in the 80's it was not illegal to overtake in the slow lane or on the right as it was over there, but it was illegal to be overtaken by another vehicle if he had to go into a slow lane to do it.
That meant if you were in the fast lane and came up behind a slower vehicle, then a quick flash of the lights would have them scooting over to the slower lane very quickly.
If a flash of the lights did not work then you just needed to indicate that you were going to change the slower lane and they moved over pretty quickly.
In those days it was policed very heavily and was very effective in keeping traffic to the slow lanes and kept traffic flowing.
I have suggested that Qld Transport trial it on the M1 but met with the typical WTF would you know, you are just a dumb truck driver response.