This makes sense, but it's not something I thought of spontaneously as a beginner chicken keeper.I used to buy from one the local manufacturers. It was still a half hour jouney each way.
I eventually found a small agricutural supplier who mixed their own feed on the premises. They would make a mix to order. But, the minimum order was 100 kilos.
People tend to get worried about what they feed their chickens. If you keep a contained flock then commercial feed becomes more of an issue. Many people I know have never fed their chickens commercial feed and their chickens seemed fine and lived to a ripe old age compared to the majority of chickens I read about on this site.
Sure, there is more to longevity than what a chicken eats but chickens are omnivores and are very good at finding what they need given the opportnity and of course the land to hunt on.
I have friend in Hertfordshire, England who has been keeping chickens for over forty years. Apart from losses to predators (few) they live on average to ten years old. He free ranges them on less than an acre of land most of which he grows fruit and veg on.
He does buy fish meal and cracked corn and sunflower seeds last time we spoke but apart from these the chickens eat what he eats. He just cooks more than he and his partner need, sticks it in a blender and gives it to the chickens.
If you eat take away burgers and chips etc then not only are you not getting a decent diet nor would your chickens be. If you eat low sugar and salt food with proper vegetables, meat, fish etc the chickens will be fine.
Chickens don't need anything special. They need the same amino acids we do. What laying hens need is more calcium than a human is likely to get in their diet. Feed them their egg shells back in the blended human food is a good start.
However, this all starts to unravel when you buy production breeds and now very sadly many of the so called heritage breeds who also lay far too many eggs.
Too late for many but getting the right breed for the condtions you will keep them in is a very early lesson to learn in chicken keeping. In general barnyard mix types fare well with minimum fuss.
Finally there is nothing stopping people from learning how to make their own chicken feed. I don't mean following some nut job on Utube or facebook, I mean study the subject some and find out what you can get locally to make up the correct nutrition.
This is what I am slowly doing now. There are lots of feed recipies but if one just took the nutritional analysis from a decent quality feed label and worked out what foods gave these you probably wouldn't go too far wrong. by any means.
If you got a cat, a dog or a horse you would certainly realize that not all breeds require the same maintenance / environment / food.
My chickens don't free range though. They are outside all day on 400 to 500 meters sq, even if we move the nets around a bit there is always a point where they have less to forage.