If EVERYONE stays home, how do stores remain open? Do we think they are run by robots?
I try to use language with some degree of precision. I said "assume no stores will be open during that time". ASSUME, not "stores will definitely be closed during that time". Assume, as a part of planning, not categorically know, because the assumption will make for better planning.
It is far safer to make this assumption and be wrong, than to discover not making the assumption was a mistake.
In the first case you end-up with extra food and supplies you did not need and will simply consume over several months (or donate to the Red Cross, which would be fantastic). In the other case you and your family could suffer greatly due to being utterly unprepared.
Maybe it's my aerospace background...I have learned the hard way that ignoring potential failure modes and corner cases is the mother of all fuck-ups.
But when people are reacting to the coronavirus, the implicit question isn't what preparations are good to have for general worst case scenarios; it's which preparations you're likely to need, which ones you can no longer afford to be without. As many a doomsday prepper will attest, there's always one more contingency you could plan for, but telling people to start with extreme measures makes it less likely they'll plan at all.
Assume stores will be closed. Plan accordingly. Be glad if things don't play out that way. No harm done. Not difficult. Not extreme. Not a big deal. Just reasonable assumptions and planning in the face of what could be a very serious event in human history.
I can't even buy dust masks at my local home improvement store as they are out of stock. And that's not even a necessity!
Nothing wrong in being prepared for an emergency.
Having lived through at least a couple of important earthquakes in the Los Angeles region I can tell you, without a shadow of a doubt, you do not want to wait until the last minute to get ready for any kind of an out of the norm situation.
Then there's the question of what would constitute responsible behavior in the event of COVID-19 getting more serious in the US. I would guess this would, at a minimum, include preparing to stay home for somewhere around 30 to 45 days, particularly considering that we are starting to think the incubation period could be as long as 27 days.
And so, from this perspective alone --that of being a responsible citizen-- I am not equipped to understand someone who would down-vote advise to prepare for 30 to 45 days of at-home isolation.