Don't have pets, but if I did. Not sure.
I think it depends a lot on who your pets are and what their place in your life is. My brother has 5 acres with alpacas and dogs to chase away the coyotes. It would never occur to him to buy his dogs presents. I live in a regular house. My dog sleeps on the sofa and is a family member. It would kill me to not get a little something for my fuzzy buddy.