Q: Why Overclock?
A: The reason behind it is very simple. It is to improve a computer's cost performance index by maximizing computer hardware performance. For example, with an overclockable CPU working in a stable system environment, the speed of such CPU could be increased to be the same or close to a faster rated CPU on the market after proper overclocking. From users’ perspective, besides the significant gain in performance, to be able to save huge bucks while still being able to enjoy the performance of a high-end system is the key.
So honestly, the question is not why, but why not?