Volcanic winters are far more frequent than catastrophic asteroid blasts. Disregarding a volcanic winter possibility and its impact is like disregarding the possibility of a pandemic.

> Volcanic winters are far more frequent...

True. But if you're working in public policy in a vaguely-democratic country, and trying to get anything useful done - then the public feels vastly more familiar with "giant asteroid wiped out the dinosaurs" than with volcanic winters. So, just like "Zombie Apocalypse (wink)" disaster prep - you go with a "close enough" scenario which lets you achieve some actual preparation.