I think you underestimate the amount of bad health environments there are in cities (anecdotal evidence only). I would not call most cities or working environments anywhere close to sterile.
I grew up muddy and dirty, eating anything I found in nature that was mostly edible (apples, ground cherries, berries, chewing bark and grass), as well as organic beef and pork (before we knew what that meant) and garden vegetables. That was closer to historical experience.