However, we don't all live in areas where there are rats roaming about. One of the few advantages of living in neighbourhoods that are a little further away from downtown, is that suburban yards tend to be larger, and many of us have never had to worry about rats rummaging through our trash. It's doubtful that rats would be an issue to those homeowners if backyard hens were allowed.
Besides, as this Grist article points out:
It is not something that causes a nuisance to anyone except for the chicken owner.