If you knew the alert could be about something hundreds of km's away, and that it usually is, it's very likely people would instinctively turn off the very loud alert instinctively. There's a reason why "alert fatigue" exists. And it has been documented in tons of different settings. Too many alerts and warnings are worse than none. Is there any reason to believe the same phenomenon wouldn't happen in this case?
Yes, because they happen so infrequently and are widely known to only be used for alerts that most people think are actually important, even if they aren't always relevant to every recipient.
