If they don't keep them maintained, they break down. Just like a car. If you don't keep it up, all of a sudden you're staring a big bill in the face.
It gets real hectic. If people bring them in early, there's time to do it and do it thoroughly and correctly, instead of rushing to get them all done, so everyone gets them back quickly.
The air molecules pass right through the rubber molecules, even without a puncture. People never keep the tire pressure up.
You can't stop the wear. But, you can slow it way down.