Most popular pets

I think one reason why there are more cats than dogs in a household is simply that cats breed faster and more easily than dogs.

A bitch comes into heat only once in every six months. A tabby is nearly always ready for business. Plus dogs are very often kept on leashes whereas a cat on a leash is the exception. So the chances for dogs to find a mate is very limited while cats go in and out as they please.

Of course, size must be a factor, too. You can fit more cats in the same space than dogs, generally speaking.