Been reading around a bit (such as here) and it appears that base gun-free zones were applied even before 1992; the policy was made official DoD wide. Some bases were gun-free before the policy was made official by Bush Administration officials in 1992.

And at least among the sites I’ve read through (this being one) folks commenting about firearms on base note that this is a sound policy, not arguing for anyone to carry.

Why was the policy enacted? It’s right there in the directives (and the directives that reference it):

“[T]he necessity to carry a firearm shall be… weighed against the possible consequences of accidental or indiscriminate use of firearms.”