Well it depends if parents don't have two pennies to rub together due to recent job loss.
In normal circumstances, it's cheap enough to provide toast, beans on toast, cheese, jam, ham, spread sandwiches. Noodles. Cooked pasta with some tinned tomatos. Asda do garden gang fruit for no more than a pound for a pack of apples, pears etc. You can be creative on a budget. For example. Pasta, £1 frozen mixed veg and cheese. My kids love it and the veg lasts at least 5 meals. There are many ways to feed children something. Fish fingers and mash. Pizza. Macaroni. Tinned soup. It's all very cheap, especially if you get own brand.
But I understand there's poverty. We've never had to experience it. But I don't doubt there are many families trying to live of £40 a week for food. Or worse.
In some cases people probably just don't manage their money or they can't cook or be creative. But the amount of people using food banks speaks volumes.
Also life is just expensive. It's uniforms, new shoes, new coats, technology, constantly having to pay for things for school events. Running cars, houses etc.
My partner's currently loosing £250 a month due to overtime being banned. Since march we've lost about £2000. Which is 5 months of the mortgage. It's hard for people right now.