One theory is that a cat's fang teeth are vestigial-in other words we've so domesticated the cat, evolution no longer 'favors' their super-sharp teeth! I think plain wear n' tear is the culprit. If you've seen a picture of an old tiger,it's teeth have dulled with use. A cat's teeth wear down,as opposed to decaying. Something seems to accelerate the process in the American Housecat .