It is weird for the traditional view of pets as property, beasts of labour, ornaments, or other living in-person. However recent decades has seen a popular shift towards treating select sentient animals (experience emotions) with some degree of sapience (reasoning/higher cognition), like cats and dogs, as people. Humans treat them as individual persons with their own subjective experience, desires, and lives worth living.

So when a human adopts a non-human animal under this view, they are also taking on the responsibility to care for the animal’s needs and we’ll-being, not just for what the animal provides the human (as would be the case of a beast of burden) but primarily for the sake of the animal’s own worthwhile life–the human takes on a guardianship/parental role. This is why people are more and more being referred to as mom/dad/parent of their pet. More and more people are adopting animals as non-human children. Vets like to enforce it because it reduces animal cruelty and makes people more likely to do basic care.

This isn’t to say many farmers don’t try to give their animals a good life or recognize them as feeling beings with their own personality. They do, but not to the same degree as treating a pet as a non-human child.