The U.S. Air Force doesn't agree with you. In fact, Firefox and Mozilla are banned from their network. IE 6 is the only authorized browser.
Stand by for the conspiracy hawks....
It wasn't at CENTCOM, which is at MacDill AFB....
The US Navy also tried replacing all of its custom onboard operating systems on its ships with stock Windows NT. Doesn't mean that they knew a damn thing about what they were doing at the time.
We have a time keeping app that requires ie6, this does not make ie6 more secure or easier to use than firefox, it just means that this app uses things that only render properly on that engine. Your logic that people who use it think its more secure if not very good..
The other reason for desktop standards is simplicity, even if all but one app work fine in multiple browsers you want to keep an attack profile as thin as you can so you limit it to the one browser. Hell I dont use ie for anything but our time collection (I dont use windows for much more than that) but out corporate standard for non it folks is ie only because of that one app..