Once again...
On single lane roads you must drive as far to the left as practical (except motorcyclists). On multi-lane roads if the speed limit is 90km/h or more you must drive in the left lane. This same rule applies to any road where there is a ‘keep left unless overtaking’ sign. On these roads you can only drive in the right hand lane if:
- you’re turning right or making a U-turn;
- you’re overtaking;
- the left lane is a special purpose lane, e.g. bus lane, bicycle lane, slow vehicle turnout lane;
- the left lane is a turning lane and you are going straight ahead;
- you’re avoiding an obstruction;
- you’re not driving a vehicle of a type that is prohibited from the right lane by way of signs (i.e. trucks);
- the other lanes are congested with traffic.
We don't have 4 and 5 lane roads for everyone to sit in the left lane at all times. That is literally not how they are designed to work.