Depends on what kind of information the system needs to feed out. Just one example off the top of my head, a calculation to tell you how long you could hold a negative angle of attack before hitting the ground might divide by altitude somewhere in there. No, that would be dividing by velocity. Well, I'm sure there's something. I don't know why sea level is a factor--I'd be going by distance from the ground, probably working with a radar altimeter in the loop somewhere.

Of course, I've never worked on military planes. Maybe a radar altimeter in a fighter is just a big, wide radio highway for a missile to climb up.