If lots of people try to buy extra things all at once, all at the same time, at just the same time as everyone in the supply chain faces huge logistical problems getting supplies into the shops/out on delivery, of course it creates shortages.
For the umpteenth time, that's not what's being described here.
There are lots of possible approaches to feeding a household. Some people here imply that they buy what they need for a week and at the end of that time they have next to nothing left in fridge, freezer and cupboards. That's fine, as long as you can get out smartish to buy the next week's supplies.
If something happens to prevent you getting out, and you can't get help from anyone else, you're in a jam.
My approach, which appears to be the same as that of many preppers, is that routinely, crisis or no crisis, I buy more than we need for the week. The perishable food gets used up (I waste very little). The non-perishable food won't. After a few weeks of this my cupboards have tea, coffee, pasta, rice, oil, flour, sugar, tins of beans, soup, tomatoes, herbs, spices and so on. My fridge has odds and ends of vegetables, sauces, butter, cheese. My fridge freezer has meat and fish bought on special offer, veg, meals I batch cooked that just need defrosting, an extra loaf of bread. The bathroom has an extra pack of loo rolls. And so on.
This isn't panic buying. This is basic organisation for us.