For "knowledge workers" as most of HN is, they can just not show up today and then do today's work tomorrow. But something like a railroad ceases to function at some point and that has severe repercussions.
Now likely the "railroad" problem could be solved with some work, imagine a nation-wide company that handles railroad staffing emergencies, with on-duty employees available to go to a stranded train at a moment's notice. There's some dollar amount this would cost (even if you utilized jets and helicopters, those are just a cost) and it'd work. But that cost is what the railroads don't want to pay, as they could also do the same thing by hiring more employees (and have some percentage of them "idling" at any given time).
