OUCH!!!
Anyway, why are people panic buying and stockpiling??.....Because that's what people do, tell them not to do something and it's the first thing they do.
I was guilty of that once, well if you could call it stockpiling, in the mid seventies there was a "rumour" going round there was a shortage of sugar {remember that?} that's when I worked for a local well known bakery as a salesman and having two small kids in those days plus I had two heaped teaspoons of sugar in my tea. I gave most of my customers {shop keepers} a sob story and they kept me supplied with bags of sugar. We didn't have tons of the stuff but enough to pass quite a bit onto friends and family especially those with kids.
I'm the first to admit that since then I have always had stock of the essentials, especially those with long {or no} sell by dates, bog roll, kitchen roll, bleach/cleaning stuff, toothpaste, tinned stuff, freezer stuff, and funnily enough just a one pound bag of sugar lasts us a year now. This is done mainly due to the fact when I worked my missus could shop without lugging heavy cumbersome items back from town on the bus, as she doesn't drive.
When it comes to things like this the vast majority of shoppers go into "selfish" mode, and the rest find themselves having to follow suit or run the risk of not getting what they want.
All shops should be made to put a limit on ANY item being bought irrespective of shortages or not.