It is possible to manage on a shoestring budget - everyone knows that because there are endless articles about it, and 'experts' showing just what can be done with a bag of rice or pasta, etc, etc.
But what's missing from these is context. Some poor families will be faced with a lifetime of impoverishment for all sorts of reasons like chronic ill health, mental-health problems, low self-esteem, chaotic life-styles, addiction, unstable family environment, depression, etc. The daily grind of poverty makes it very difficult, if not impossible, to pull yourself up by your bootstraps and traverse 4 different supermarkets to get the cheapest offers; to return home and find the enthusiasm to put together all the ingredients and make yet another meagre meal. There are no treats, there is little joy - you might be living in inadequate accommodation, an unheated flat. Your whole life is devoted to making ends meet and thinking about 'what if' - what if the children need new shoes, or this or that breaks down. You may even be working at some low-paid paltry job, or on zero-hour contracts, but all that will do is reduce the amount of your benefits, and if you have neither the skill nor credentials to take on a higher-paying job, that's your lot - that's your life... an interminable daily struggle to put food on the table and simply exist.
Anyone can manage on £20 a week to feed a family for a month - it can be quite interesting to see how inventive you can be. Before you go back to your well-paid job and warm home. But try doing it for life, or the foreseeable future, with little hope of extracting yourself from low-paid work in a home environment that is possibly inadequate, cold and damp. People need hope, and they need jobs that pay enough to live on - even if that means the rest of us have to pay more for some of our goods and services. When we are offered these goods and services at rock-bottom prices, it's because someone is being paid rock-bottom wages. And we're subsidising such employers by topping-up the wages of these employees with tax credits.