It necessitates that all of those families buy twice as much this month so that they're prepared to spend a few weeks staying home starting the day before they would have gone shopping again. It also necessitates that I (a single person living alone who normally goes grocery shopping every other day or so) buy way more than I ordinarily would. Most people are not out there buying truckloads of TP. Everyone buying twice as much TP (and everything else) as usual is more than enough to create shortages.