The old fairy stories have a valuable function. They show us cruelty and horror, yet they speak to the hope in all of us that goodness will prevail.
The majority of all old fairy stories is to make the audience perceive that innocence will always overcome evil. Multiple ways that old fairy stories do this is by punishing the bad and rewarding the good. In Cinderella by Anne Sexton the twins which were usually recognized as the evil of the story were punished by getting their eyes pecked out by a white dove. Since Cinderella was the innocence and purity of the story she was rewarded with with a happy, wealthy marriage that lasted forever.
In Cinderella by Anne Sexton, the archetype that goodness will prevail serves a purpose to the readers.