Social expectations. I raised a few pigs in 4H and while they were as smart as dogs, they were raised to be eaten and after being sad about my first one, the established idea that they exist to be eaten made it different than a dog who existed to protect the animals from wild predators. Heck, outside farm dogs and cats also have a different relationship than indoor dogs and cats becsuse of how everyone treated then when I was growing up.
So while I known in my mind that dogs raised to be eaten are seen in some places like pigs are here, it is just established as a different thing socially. Kind of like how many people are averse to eating squirrels and rabbits because they see them as small animals that hang out in their yards, not a food source.