When I lived in Jakarta the issue was that tap water wasn't drinkable, so in case of flood or earthquake it was important to have a supply of drinkable water.
When my son was a baby I bought a heap of bottled water and put it in the kitchen cupboards. And told my wife that it was for emergencies only. There was enough for a week at least.
Most households had a water dispenser like the water coolers that offices used to have, with the big 20 litre bottle.
One night, around 10 or 11 pm and all the supermarkets and convenience stores were closed, my wife said to me "we run out of water and I need to make milk for the baby, can I use tapwater?". I was was like O_O, no, that would make an adult very sick and possibly kill a baby. I said "it's okay, just this once you can use the emergency water".
My wife said "I already used all that". So I ended up walking around the dimly-lit streets looking for a late-opening street food stall that had extra water (I found one).
In other words, we are not big on preparation. We could probably last a couple of weeks on random canned food.