Unloaded weapons are more common than most people think.
The actual issuance of ammunition is very unpredictable for security and support troops. Sometimes political motivations trump safety. Sometimes an entire unit will have their munitions taken away, due to a single idiot that had a negligent discharge. Sometimes, the weapon itself is expected to be a better deterrent than the need to use it.
Everywhere you go, the rules and situations are different.
"Such is the strange way that man works -- first he virtually destroys a species and then does everything in his power to restore it."