From what I understand, a lot of those old tales were never children's stories at all, back in their origins. They were just general folklore. Somehow those "fairy tales" got watered down into becoming children's stories over time. Examples in this tangent include The Little Mermaid, Sleeping Beauty, Cinderella, Snow White.
Might apply to some of them, but not the Little Mermaid as the last page of the original manuscript as modified by the author is basically emotionally blackmailing children (the Little Mermaid can go to heaven sooner if you are good little boys and girls).