I'll take a jab at that, and I'd frankly say that it's ~nonsense~ that we're living anything like they did during WWII and the "air raid" lifestyle. There's no blackout drills and no bunkers. We're not rationing food or steel or rubber or nylons. Except for the TV, you would never know that we're at war, and desperately so.
I would also argue that a "go bag" is an essential bit of preparation, whether it is just a few key items or a whole army-surplus-store in a box. The reason to keep it in the trunk of your main driver car is not so much to be ready to bug out from your house, but to ensure that it is with you when ~you~ are not at your house.
It's not just about terrorist attacks. It's just a sensible collection of stuff to make sure you've always got. There's any number of emergencies that can develop rapidly... especially depending on where you live. An earthquake, tornado, flood, volcano... and sure... a major bomb event. Heck, I've gotten into my kit when I was stuck at my office due to a snowstorm that gridlocked all the roads. Came in handy.