A better question: if animals have souls, why don’t they have spiritual/religious rituals, or for that matter religion in the first place? There’s really only so far you can go on the “everything has a soul” argument before you end up in pantheism.
Animals are referred to in the biblical creation account with the term nephesh which is spelled exactly the same way as the nephesh which is the human soul. Rocks, oceans, trees, &c. never get honored with the term nephesh. Never.