@Gargron I think at core people are like "it would be really unpleasant to run out, and I'm not actually sure how fast I use it because normally I just buy some when it gets low and I better grab it while I can."

In the US, at least, a temp shortage doesn't even have to involve buying multiple packs: they're so bulky and low-profit and (normally) predictable that stores really don't carry that many actual units. It doesn't take many people buying *one* pack but early to screw it up.