As an addendum to the last entry, I’ve thought of another way of expressing what is going on there when wearing shoes:
Your feet have independent front and rear suspensions.
The front axle is at the ball of your foot, ahead of the arch; the rear axle is at your heel.
When you put on shoes, your feet no longer have that independent action. Instead, they are really more like a toy car, with a single axle that runs from side to side in the front and another in the rear. The tires are locked onto each axle and have no independent action. The front and rear axles are also pretty much locked together. If a real car was still designed that way, it, too, would show all sorts of weird tire wear. Shoes do the same thing, and we see it in the wear on the soles.
That’s not how feet are supposed to work. They really do have independent front and rear suspensions that can compensate for all sorts of terrain, and peculiarities of our bodies.
As an example, about 5 years ago, I was forced to wear shoes in a building (I had to go there, and they had a rule). While there, I turned, my foot caught in the carpeting (because of the footwear), and I shattered a bunch of cartilage in my knee. After a bunch of expensive MRIs and rehab, it’s (mostly) usable again.
However, since that time, I have extra-thick callus near my big toe, and only on that one side. My foot is compensating for the fact that my knee has those problems, and that foot can do it because of its independent suspension. When I am forced to wear shoes, I find that it really bothers my knee, because my shod feet can no longer compensate. That’s what the independent suspension is good for.