But he was.
What's the biggest disadvantage of having a gun that you aren't obligated to use as you crawl in fear and know the crazed gunman is armed and armored? A man in armor isn't a reason not to have a gun. It's just a situation where your tool isn't useful. Hopefully you've been trained to use it wisely and you don't try it until you have a very good chance or if he's coming for you.