Your point is very well taken. I live in a city ringed by some 7 military bases, with some very nasty things there apart apart from being prime "terrorist" targets (I always put "terrorist" in quotes these days -- became I'm not, and don't anybody should be 'terrorized'). The only advantage I can see in splitting is avoiding the chaos that would follow a really nasty event. More on the level of being simply tiresome, after a while.

This community has a truly nifty flood every flood every few years with resultant loss of life, etc., etc., and the populace has proven to be remarkably resilient. But, the drumbeat of all emergency authorities in such events is STAY PUT. Do not put yourself and potential first responders at risk by getting out in it. About half of the fatalities we have had from storm events over the twenty years I have been watching it has been folks that had no business being where they were when they got killed.

In days gone by, I had to get out in the stuff when it was happening, but, thankfully, no more. I should, thus, term my 'BOB' an expanded boony survival / urban personal convenience bag. Its survival components are very unlikely to ever come into play unless I'm already out & about.