Each year something goes extinct. Creature that survived a million year, experienced so many changes for survival, evolved into what they were, got lost. No way to recover their features, their abilities are lost to the ground.
This is a big loss.
They also have a domino effect on environment. For example,the reintroduction of a dozen wolves in the Yellow Stone national park solved the over grazing issue from the deer. As they became aware, they started moving more cautiously. This in turn helped the plant and the deers themselves. So next time when you hear something go extinct, Mourn It. Something that is endangered, act now.