Comment by MichaelRo
Definitely it's not about the cost and convenience.
And I haven't seen it discussed much, which tells a lot that the HN-ers are city dwellers with little experience in the countryside life. But the biggest, nastiest, deepest problem with anything animal is ... shit.
Animals produce shit and lots of animals produce loads of shit. And chickens don't have the notion of "this area is for eating, this one's for shitting", they will shit all over the place. So if you don't enclose them and can run to your porch, they'll shit it up so gotta be careful where you step or sit on. If you enclose them, better be prepared to wipe shit of your boots coze no way you can avoid it forever. Then the "pleasant" activity of cleaning up loads of shit from the chicken coop and dispose it somewhere.
Overall, having lived on a farm, my childhood memories of interaction with animals resume to "lots and lots of shit everywhere" :)
At the backyard scale it’s not so bad. My neighbor just mixed it into a big dirt pile that we all use for fertilizing our flowers and shrubs.