It is important because it is ethically wrong to cause purposeful harm to an animal, just because they are "less aware" than humans. As exemplified by this quote:
Ask the experimenters why they experiment on animals, and the answer is:

“Because the animals are like us.” Ask the experimenters why it is morally okay to experiment on animals, and the answer is: “Because the animals are not like us.” Animal experimentation rests on a logical contradiction.
Charles R. Magel