Those hatcheries are also indoor only, the chickens never see the light of day, and every person and object who walks in must be sterilized. Personally that is NOT how I want my chickens to live! Being outdoors puts them at all sorts of risk, including disease. But the whole reason I want to keep chickens is to offer them clean, natural living and that includes being outside! I want them to live as they were meant to, in nature. And sure, that poses risks. If I wanted eggs from chickens kept indoors only and lived out unnatural, sterilized lives, I would buy eggs from the grocery store.
Ditto