Earlier quoted context omitted.
Pigs have personality too. But most people would never know it given how livestock are treated.
Dogs have co-evolved with humans for tens of thousands of years, and demonstrate traits and behaviors that makes it much easier for humans to empathize and socialize with them. For example, you can tell when a dog is happy because their facial expressions resemble a human smile. Not so with livestock. Sure, you can figure it out after spending time with them, but it's inarguably not the same thing.
You can find the same exact "smile" in goats, sheep and pigs, they're definitely not making that face because they're happy.