These organs were useful to our ancestors, and remain because they do little harm to us now. B. Nature's cruelty. Out of dozens of hatchlings, only a few survive till adulthood. Mites that eat their mother alive. Black widow spiders that kill the males.
Birds eat worms.
There's lots of competition, sometimes fierce competition for food. Birds eat worms. On the other hand, natural selection has no problem with these observations, because natural selection has no good intentions. It's quite plausible that an imperfect watch was designed by a human designer. The purpose of our lives.