Perhaps you aren't familiar with these Military installations, their make-up and purpose.
Unlike a "Fort" or Camp being used as an operational base in a war zone or nearby areas for staging, these posts are small cities for troops and their families to train and live normal lives.
While there is security at the perimeter, the fort itself is housing, schools, stores, classrooms, hospitals and more remote trainig areas.
It hasn't been necessary to be under-arms except in paymaster duties and similar functions liable to interferance.
Like most of use, when our military is not deployed, it doesn't "carry" as a matter of course when at the classroom, takinng the kids to ball practice or filling out paperwork at the "main office".
In this war without fronts, It looks like that policy will deservedly be under review.
We had enough live nukes to blow up the whole f**king world, though, so we weren't completely unarmed.