Let's not fool ourselves. The US Military is institutionally afraid of weapons. The (overwhelming) majority of US bases I've been on in Iraq and Afghanistan have clearing barrels at the gates. Service members in combat theaters are often required to walk around with cleared weapons because loaded guns are scary. How do you think that Afghan AF officer was able to kill 8 NATO troops (and a contractor) in 2011? Those poor bastards had empty weapons. I have to carry a letter signed by an 0-8 equivalent that says I don't need to download my weapons coming onto bases.... in Afghanistan..... Most soldiers don't have that letter. Wrap your brain around that.
Here's the underlying problem. For the last decade or so the US military has developed a culture of risk aversion. Officers and senior NCOs are often afraid to make a call because a bad call means the end of their career.
Last year I had to sign a letter exempting an O-6 from responsibility before he would let me leave the base to do my damn job. Mind you, I didn't work for this man, but he was so concerned that he'd get blamed if something happened to my team that he wouldn't tell the guys at the gate that we could leave until he covered his ass.
Any base commander that allowed service members to carry on base (outside of official duties) has to be willing to accept that any incident means the end of their career. I don't see that happening. Ever.
And that's not even addressing the piss-poor small arms training most service members have.