Others may not though. The point remains that it should never be used except for emergencies and as others have pointed out this tone can trigger other things to happen as well which can then in turn create an emergency.

Well obviously not because you still recognise it and know it to be in use for an emergency. You aren’t desensitised. Just because you may not react doesn’t mean you are desensitised. You still know “that’s an emergency”. If it’s being played all the time in movies and tv and such you eventually hit a point where you stop thinking emergency and think “eh just a movie”. Your brain stops recognising it as an emergency sound and as just a sound that’s recognisable but not anything to worry about.