If you do not have pain, then
If you do not have pain, then there is no reason to.
Most people who have knots in their muscles, usually have the same reoccuring knots in their muscles, which can be due to a variety of things, such as over-use of the muscle and it's corresponding ligaments, repetitive strain injury to the muscle and it's corresponding ligaments (usually from repetitive jobs), and of course accidents and injuries to the muscles and their corresponding ligaments, etc. Also, anytime there is a musculoskelatal imbalance -such as a twist in the hips, or a short leg, etcl, muscles tend to get knotted in response due to the uneven strain on the ligaments from the imbalance.
So "some" lucky people just have not encountered these types of problems, or not many, and may not have any knotted muscles, or at least not chronic ones. As for the rest of us - we suck!
Most people have some knots in their muscles and do not necessarily realize it unless they start poking around. The benefit of getting out knots is to increase your musculoskeletal alignment, which, with regard to racing will make your body more streamlined and should allow for faster speeds.
It is important to note, however, that you do not always get rid of knots by actually working on the knot itself, though that can work. A more efficient way is by learning where the trigger points for the painful muscle are and working on those points (they are not usually on the painful muscle).