Social Hierarchy of Animals

In our culture, there is an obvious social hierarchy of animals. Animals that are common household pets such as cats and dogs, are treated human-like or as "a part of the family".  We give them special shelter, food, and even treat them to privileged healthcare.  Furthermore, we look down upon other cultures that decide to consume animals that have a higher social status. Domesticated animals receive many benefits that many animals do not. Most pets do not provide any benefits as where as a cow that provides many resources and benefits is not treated as fairly and with so much regard. But why do we only extend our empathy to certain animals?  Why do we treat some animals as "pets" and other animals as test subjects and food?  These rights of socially higher domesticated animals can reach farm animals, experimental animals, and maybe wild animals.