Pets vs Slaves

I'm interested to know what the community's view on Pets is. From the bit that I can find, Pets are not really a recognized class or subclass. I'm curious as to why this is? (unless I've been misinformed) Pets, in my mind, seem to play a very different role and have a somewhat different set of rules than slaves.
I know personally that I treat my pet in a very different manner that I would a slave. He isn't a "pet-play" pet- I don't dress him up as an animal; He is a human pet, though he doesn't do housework and he does curl up in my lap and purrs when petted. He is disciplined- quite harshly when the need calls for it.
So, rambling nonsense aside, I'll reiterate my question. What is the view on "pets," human or petplay? And why?

Yes human pets are a type of slave but not all slaves are pets.
I have no idea about "official" terms but in my view, To me it is a service slave that would do the housework and want to have clear rules to follow. While a pet slave is more playful (rather than bratty), by that I mean follows rules but will act out to get attention.