Tucson has an ordinance that requires one to have kennel license, in order to own more than 4 dogs. I'm not sure about cats. This does address the health issues and keeps the hoarders under control. Fosters and rescuers are covered under a separate ordinance.
This definitely seems to be fairly widespread. Everywhere I lived in the U.S., and where my family members are living now, had/has limits to the number of pets. It's done to prevent hoarders and annoyed neighbors.