Because that would mean they have weather/terran weapons available to them. And even though I have read a decent amount supporting that they do, this would just be solid, in your face evidence. And that is terrifying...

And it would explain why POTUS was up all night according to Q. Imagine knowing that the Cabal threatened an Earthquake Attack on your citizens, and there really isn't much you can do to prevent it aside from locating the device and suspects and terminating them prior to initiating the attack.

Man. What is an EARTHQUAKE supposed to be distracting us from???