Actually, for many parents, leaving their children at home or in the car just isn't an option for one reason or another, whereas one doesn't have to have a dog with them everywhere they go. If the weather is conducive, dogs can be left in the car without someone calling the law. Children...
When did chickens become exotic pets?....I'm thinking about the same time they became "pets". Most country vets never saw a chicken before then because farmers knew that chickens were cheap livestock and weren't worth a trip to the vet, were easily replaced and were easily culled for illnesses...