I read through this and don't think anyone has mentioned this.... or I'm just mistaken. But I think real railroad wheelset are also this way in order to center the car even on the straights. It keeps the flanges off the rail. Instead of relying on the flanges alone, which would wear them and the rails out faster, they use tapered wheels that make the car roll down the tracks without the theoretical need for the flanges. Of course you must have the flanges because the taper is not enough to keep the cars on the rails but it does work. In the image below you see the flanges aren't even touching the rails!
Below is a picture of the theoretical wheelset without flanges. It would ride down the rails if everything were perfect. It just wouldn't go through switches well.
