They may not be self-aware, but it seems reasonable to assume that animals like dogs (for example) have inner lives, after their own fashion, and are capable of experiencing qualia. Certainly more reasonable than to assume that they can't.
It's probably because the only animals YOU ever see are the ones in your dining plate. If you studied animal behavior a little you'd maybe realize how wrong you are.
I guarantee you other animals are first-class conscious. I can't prove it to you, but that's a problem with epistemology, not a problem with the other animals.
They may not be self-aware, but it seems reasonable to assume that animals like dogs (for example) have inner lives, after their own fashion, and are capable of experiencing qualia. Certainly more reasonable than to assume that they can't.