I was thinking more from the perspective "make them out of materials that aren't too bad to inhale/ingest"

What material is strong, malleable, dirt fucking cheap, has a high coefficient of friction, easy to work with, amenable to additives, meets all the suspension properties we expect out of a tire, etc, and isn't bad to breathe a lot of the dust of?

Modern tires are works of material science miracle, working with dirt cheap inputs.

Even iron dust from steel on steel friction like with trains is bad for your health.

The human lungs just have bad filtration.

Sure, that's great too. But the rubber lasting longer means less of those bad things to inhale floating around at any given time.