That's why variations of the same tales and motifs are found in every culture and in every historical period. In Jungian terms, they are the purest and simplest expression of collective unconscious psychic processes. Fairy tales describe the basic structures, dynamics, and processes of the human psyche. And these are highly complex, morally ambiguous, and often lead to unhappiness and tragedy. Anyone who has to deal with the psyche and its effects on human life knows this very well.
Fairy tales depict various aspects of the inner psychic drama.
Life takes strange and perverse twists and turns. Figuring our what life is all about is often beyond our rational capacities, so we turn to stories, to novels and fairy tales, folk tales, legends, and myths. Out of this rich milieu we consciously and unconsciously find themes and subplots for the life we live as adults. Robert Bly, the poet, uses fairy tales in his public readings because they tell us something about psyche, the internal imaginal landscape. Cinderella, for example, is not only a children's story, but an adult source of imaginal figures that we carry in the underground stream of our own imagination.