Everything has a lifespan. Scientifically, it can be said every set of molecules can have a "half life." The degradation of the atoms or molecules can be measured. Now those measurements tend to be in thousands of years sometimes. But things like watches,...
It's not magic, it's just the normal aging of materials. Dials are usually made out of steel and what's called "patina" is basically rust Unless you live in a air-free environment like outer space, there'll always be inside some air the watch