Folk tales are instructive. They caution readers/listeners about the consequences of certain kinds of behaviors or attitudes.
Characters are not complex. Instead they are stereotypes: the thief, the liar, the clever youth, the evil stepmother, etc.
Even when written down, they are sometimes told in a way that sounds like the spoken word: directly addressing the reader, use of dialect or slang, etc.
The structure may be repetitive. Things that happen in threes are common. Repetition of lines is also common and would have been helpful to whoever was memorizing and telling a story in the oral tradition.