Martial Arts Weapons

Martial arts without weapons is not commonly considered as complete martial art. Most of the martial arts includes weapon training under their system. Many of the weapons are common weapons and some of the tradtional martial art systems have their own unique class of weapons. Chinese Chain whip and Urumi of Indian Martial art Kalaripayattu are a few of them. Martial arts weapons ranges from tiny nina throwing stars to long chinese rope darts. I am wondering why guns could not be added as a martial art weapon.