Why? If everyone followed the rules the lanes would segment into slowest on the right, with gradually increasing speed to the left and people moving between the lanes as needed to overtake. It would be far far far better than the chaos of having to move across all the lanes of traffic all the time because there are random campers driving below the speed limit in every single lane.

First, everyone switches right as soon as there's a gap in a righter lane, so lots of unnecessary switching. Second, the right lane is always full making it hard to merge on or off the highway. Third, the leftmost lanes are underutilized when they could be filled with people who have a long way to go until their offramp.