Basic necessities are important. You never know what is going to happen. What if there are many people sick and utilities don't function as a result of the staff not being there? It's possible that water might be cut off because there is a leak and no one there to fix it or whatever, or shipments of things they need are delayed.
But we do have some idea of what is going to happen, even in a worse case scenario. For example, let’s say that everyone finds out that 24 hours after dying of Covid19, the dead awake and want to eat brains. The zombie apocalypse is actually upon us. All water facilities are abandoned. Perhaps they will be staffed for the next day, but likely people will bugger out of there quickly. Even then, the water will be on for a few days at least. It doesn’t just shut off. There still water in the towers, and water will still flow to the towers for (probably) weeks before something shuts down. Nevertheless, I have days to grab whatever containers I have available (and I have plenty) and fill them with water. Hell, I would fill the tubs too.
Food? That’s a different story. There is a 2 day supply chain - max - for food.
I guess what I am saying is that I’m seeing people leave the food and buy the water bottles.
They need some food, and for Christ sakes, grab some spare medicine. If the zombies start roaming, I’m grabbing my shot gun and heading to the drug store first.
What they should do it limit purchases, one or two per customer. They don't because retailers and manufacturers like the economic boost it gives them - they don't care who buys it as long as it's bought.
And water is low hanging fruit. It’s a waste. Buy food. Buy medicine.
There's also the issue that the bulk packs of toilet-rolls are big and bulky so empty shelves are easy to achieve and more obvious than when a smaller shelf of some item is out.
This too is odd to me. Ok, so back to worst case... zombies are out and about. Toilet paper will definitely be limited availability soon. Grab your shotgun and run to Home Depot. Snag a bidet. That will keep your ass clean for the remaining time we have water pressure, as well as the toilet water.
Obviously at that point you are OK, but you would need a plan to get out of town and find natural resources.