You've got this function all wrong, The tire is supposed to protect the wheel, not the other way around. Wheels are more expensive, so the protruding bead of the tire is supposed to offer some protection from curb rash. Therefore, it is exposed and usually makes contact first. Maybe something jagged in the curb where you keep curbing them.The way the tires are being manufactured or what they're made of, plus the rims providing zero protection for this inner rim of tire.