Why we run?

Lot's of us run. Lot's of us run races. Why do we run? The list could go on and on with reasons. I think the best part of running is that it is so simple and straight forward, it is pure. Here is two examples of what I mean. In one video we see the adventure of running where it is not about speed. In the other we see the racing at it's best. Man vs. man with 3 olympic medals on the line. Both beautiful in my mind.