In Interview with a Children’s Librarian on PBSParents.com, a librarian named Natalie says:
Poetry celebrates the individual word, the sound of language, and the rhythm of language in a way that narrative does not. It is a fun, short, tasty morsel to share with children. I think it’s important to expose very young children to poetry because children build the foundation for learning to read through being exposed to the sounds and rhythms of language. For older children, I think poetry is a great vehicle for learning how complex thoughts, humorous ideas, deep emotions, or entire narratives can be expressed with a few carefully chosen words.