people who just don't have the means to buy even a few extra tins a week.
A tin of beans is 42p in Asda. I doubt very much there are many people in the country who can't afford to buy one small extra item each week over a number of months to build up a basic store cupboard.
Your concern for poverty-stricken 'other' people (not you) is misplaced.
Yes, there are some exceptions, such as homeless people on the streets, those in B&B accommodation, etc., who truly have no money and/or no storage, but the existence of people in such circumstances in no way invalidates the general rule that pretty much everyone needs to keep basic supplies.
True prepping is a pursuit of people with space, time and money.
Absolutely.
But we are not talking about true prepping, just keeping a bit of food and water in the home.
It is much harder for me to imagine a scenario where I'd need stockpiled water and a camp fire than someone who is more isolated and rural.
Many people on this thread have given examples.
Shops shut due to supply chain issues, payment issues, cyber attacks, floods, water supply issues, etc.
Or issues personal to you: like everyone in the house having flu so bad you can barely crawl to the kitchen. Or all your money going on some emergency like your car or washing machine or both at once, in which case dropping the usual weekly food shop and eating from your stores may be a financial life-raft.
Yes, cooking may be an issue if the electricity or gas is out, in which case you can eat most tinned food cold. But there are many scenarios whereby your electricity stays on but you can't get food from the shops.