OTOH, hay is hard to make and expensive to store, because you absolutely cannot let it get wet. If it even becomes damp it can give cows the heaves (and will give horses), and it can give farmers farmer's lung. Plus an untimely rain after you cut it can ruin a growing season's entire yield.
If you get it wet, you'll burn your barn down because it composts.
Your instincts are incorrect - at least in a rural, or semi rural setting.
Your chickens may be very safe and easy to raise in an urban environment that is free of small and medium sized predators, but outside of that environment there are many, many things that will very quickly dispose of all of your chickens - sometimes in just one night.
Raccoons, weasels, foxes, coyotes, large birds (vultures, hawks, owls), bobcats ...
In our rural area (west marin county, california) we need to be on our A game to keep the chickens alive ... raccoon traps set, elevated coop, hens locked up nightly, wings clipped so they can't get out of the run, high fence, three hot electric wires, etc., etc.
A cow on the other hand is too big for most of those animals (a hawk can't carry away a calf) and the mother (and other mothers) are nearby. They're big.