In my job, shutting machines wasn't feasible (well, they could kill the Internet I suppose). As for the rest, no one would get hurt by imminent deadlines, etc. We worked on the timescale of months, not hours or days. I can assure you: Not a single person in my building was concerned about missing deadlines if they went to the shelter.

As I said, people are people. Most people I know drive over the speed limit, because everyone does it, and because the likelihood of it hurting them is low. Same principle here. I'm all for everyone going to the shelter, just as I'm all for severe penalties for going over the speed limit. Most people, though, are OK going over the speed limit but not OK with people not sheltering when there's a tornado. It's almost always the case that such people have never lived in a tornado zone and cannot comprehend the dynamics of the situation.