That's because they don't let chickens run loose in a good sized barnyard. Chickens are omnivores, they'll eat anything they can catch, especially protein rich insects, grubs, worms and lizards. That's why chickens don't taste the way they used to, good.
Think of your chickens as the hogs of bird world, with one exception, you can't toss the nimrods who aggravate you into the section of the barnyard the chickens use, they don't dispose of them quickly enough. Throw them into the hog lot, there won't be a thing left of them in the morning.