I'm sure there is an excellent reason but...
If you accept the argument that failure to respond to an interrogation makes you vulnerable to friendly fire, why is IFF only Mission Critical but not Safety Critical? Or is this so in some aircraft and not others?
I can see that if an aircraft doesn't have IFF in the first place, then the crew are aware of the potential risks up front and plan accordingly. But it is surely a different matter if you have IFF, are trained that you have a problem if you get a warning, but the warnings aren't integrated. That would lull the crew into a false sense of safety.
Am I making sense? Grateful if anyone could enlighten me.