I try to avoid landing at military bases. They aren't very friendly if you don't have a reservation.
As for the airstairs, I've used them plenty of times. Several of the airports that I fly to only have airstairs available; no jetways are installed. You're right, they are simple to use and most passengers don't mind.
The problem with using jetways is with the number of extra ground personnel required to watch the customers while they deplane. If the passengers aren't watched, they will wander off where ever they please, and probably light-up a cigarette on the way. Many people are oblivious to the dangers of walking around an airport with their heads up and locked. Some airports, especially those that have dedicated airstairs, have desiganted walkways marked on the ramp so fewer ground personnel are required to watch the passengers. But unless the airport has a procedure in place for handling passengers via airstairs, then the airstairs probably won't be used.
Another issue with airstairs is the ever present FAA. The FAA makes the rules that the airports, airlines, and crews have to follow. The FAA also decides who gets fined when the rules are broken. Now, consider how much red tape one has to jump through just to do things the right way and you will see why most people are hesitant to bend the rules even when safety isn't an issue.
