I'm one of the handful of BYCers old enough to have raised chickens in the late 1950's. I'm not sharing what I've read about, but mostly just sharing my personal experiences.
In the 1960's two important things happened in the chicken world. The CX type meat bird took over the broiler industry. You'll virtually never see a traditional bird, on plastic, at a grocery store or in a bucket from a chicken drive in. Those days disappeared. The other thing happened quickly on the heels of this development. The super brown egg layers (think Bovan, ISA, Lohman, etc) as well as the super light weight, super laying strains spun off the Leghorn for the white egg industry. The modern Leghorn is nothing like a Leghorn was just 50 years ago.
The interest in the traditional birds, what are commonly called dual purpose birds, dropped out of sight. The New Hampshire, Delaware, Rhode Island White and other breeds virtually went extinct. The number of true bred, full bred birds of dozens of common breeds dipped to less than 1000 birds in existence.
The advent of the back to the earth, the homesteading movement, and finally the backyard movement has brought back the interest in these older, now popular breeds, BUT.... the hatcheries who have sold thousands of these birds, have also changed the game. The birds sold are not up to true type. They just are not. They are often a pound or two lighter than what the APA standard is for the breed, lay 50-80 eggs more per year than what their breed typically laid 75 years ago and often are washed out versions of what their body shape, feathering and coloring is called for in the standard written for each breed.
Broodiness has suffered as broodiness isn't a trait that is desired for hatchery breeding stocks. The average hatchery bird is said to "represent" the breed.
The fact is that hatcheries have provided an admirable service. They've produced healthy, cheap chicks and they deliver them to the consumer or to feed stores to re-sell in amazing numbers and for most of the year. They're selling a product. Does that product measure up to what the breed "should" be, according to the standard written and accepted? Umm.. not so much. It is what it is. A modern, 200,000 square foot Super
WalMart isn't exactly like the tiny little, old corner market of 75 years ago either. Times change. Some call it progress.