This practice is most often restricted to a small number of hens and does not permit roosters because of the noise. Hens are quiet and relaxing to be around. Dogs and cats often cause more noise and problems than six hens ever could.
Most urban chickens are pets with a purpose. They encourage a healthy lifestyle, provide fertilizer for gardens and education for children.
I would suggest that anyone with concerns look online at the huge amount of positive information on urban poultry-keeping.
With clear guidelines, communication between neighbours and a willingness to be progressive, this will become a reality.