The neck plays a part in parkour and/or doing any physical exercise, because you have to move your neck to see where you are going when doing parkour. This plays a very important part if you are free running, or doing any physical activity at a fast pace and you must react quickly. Therefore, an un-stretched neck could possibly cramp up or be pulled, and pulling a neck muscle does not feel good (it also makes it difficult to sleep).
Neck Stretches from a Chiropractor
Neck Stretches
