Although based on that logic I have never needed home insurance. This is just insurance really.
In my experience, if you don't have room to store things in a way where you can manage dates, then you don't really have room. That said, just three extra days worth of non-perishable things you would use anyway doesn't take up that much room.
Another way to think of it is as meals: for how many meals could I feed and water my family based on what's in the cupboard on its emptiest day, if I couldn't go out and had no water and/or electricity or gas? If it's zero, can I get it up to one, then two, and so on?
Getting stocks up to a point where the cupboards are never completely empty and there's always one or two meals in hand is manageable for most people.
Not those who can't afford it I know, but then those are the people that emergency supplies from the council should be for, not those of us who can afford it and do have room.
It doesn't matter if the 'meals' will be cream crackers and jam or tuna sandwiches made with a spare loaf kept in a freezer (buy a new one and swap out the old one about once a month). The only thing that really matters is having things you'll use anyway, because that way you can use them up as normal and replace them over time and nothing is ever wasted.
5l of water from most supermarkets is under £2 and even one of those bottles is much better than nothing (I think the standard advice would be 9 litres per person so two each, but anything is better than nothing). I'm not rural but I'd say water's the thing that's stopped working most often here over the last few years.