A big part of being able to eat economically is having the time, the energy and the option to shop carefully, to look for the bargains in the different shops and to find the best deals.
Can you do that if you are restricted to public transport? If you only have one shop within walking distance? If you can't afford the petrol to visit three different supermarkets? No, you can't.
And if you haven't learned or been taught how to look at a selection of ingredients and work out what to do with them (as opposed to buying the ingredients for a particular recipe), then you may struggle to make use of the bargains you do manage to find in the reduced cabinet or wherever.
For me, education is the key - teaching children how to budget, how to plan meals, how to adapt their plans to suit what they can buy, and how to prepare and cook the food. At least if you can do that, you can make the best use of what is available in your convenience store. You may not cook every night, but if you go in and happen to see a chicken in the reduced cabinet, you will have the confidence to pick it up and make something with it. And then maybe it becomes worth slowly (and as economically as possible) building up your storecupboard staples.
I do think we have lost a huge raft of practical skills. I go to a knitting group once a week - and women there talk about learning to knit in primary school - and knitting a pair of socks in the final year of primary (admittedly this is in Scotland, so they would be aged 11-12, not 10-11, but still). I learned sewing and cookery at school - we all did, boys included (and then we all went on and did woodwork and metalwork too) - and that meant we learned the basics, the grammar and vocabulary of cooking, if you will, as well as the basic skills. It is no use giving someone a cookbook if they don't know how to finely dice an onion or what it means to saute it, once diced. Yes, it is probably very easy to find out what it means, and to find a YouTube tutorial on how to dice the onion, but that will only happen if the person hasn't been demoralised and put off by the fact that they can't understand the recipe.
I mend clothing - and I have taught my dses to mend their clothes too - it is not always beautiful, but if a pair of jeans or tracksuit bottoms is only going to be used for their paper rounds, they don't care that the mend is not invisible, or that the fabric is puckered - but we have saved the money it would have cost to replace them. I have prolonged the life of so many pairs of school trousers, by taking up the hems, or restitching the seams in the crotch (for some reason these seams seem to fail with alarming regularity), and I have saved favourite garments of my own from the bin too. Dh usually does his own mending.
I love the idea, mooted up-thread, of giving households a starter pack of storecupboard basics - herbs, spices, stock cubes, flour etc. I would add a starter sewing kit to that - pins, needles, different colours of thread, and a selection of the most commonly-used sorts of buttons - with a simple, easily understood leaflet showing how to sew on a button or take up a hem that has dropped.