Tan uses a lot of implausible stories to make her point – like the duck that stretched its neck and became a swan. These stories are told by the mothers to explain concepts to their daughters, but are to help the reader to understand the hopes and fears of the characters.
Each narrative voice is also deeply serious, like the narrator is convinced of the power of what she’s saying. (Well, that would make sense. Read a diary and you’ll see what we’re talking about.) The topics that the narrators talk about are also not lighthearted because there is a lot at stake – daughters making the same mistakes their mothers made, feelings of resentment, feelings of inadequacy, etc. Especially in the stories that the mothers tell, the tone is very serious, because the mothers are conveying messages and lessons that they feel are essential for their daughters to learn in order to live happy lives, and make the mothers’ sacrifices worthwhile.