The average adult who spends fifty hours a year in a pew, will spend two thousand hours at home watching television. Some estimate that the average American child will spend more time watching television before entering school than they will spend listening to their parents in their entire lifetime. Illustrations are a vital part of learning and remembering. Think back to a sermon or a Sunday school lesson where you can still clearly remember something that you learned. Do you remember a series of abstract theological concepts presented in logically sound statements of scriptural premises and conclusions, or do you remember a well illustrated lesson.
Scripture is full of stories and accounts that illustrate the truth being taught.
Christ taught with parables. Much of the language of scripture is figurative and illustrative rather than literal. Here we have both a literal description of creation and figurative picture of good and evil. We seem to learn best by experience, and illustrations are ways for someone to vicariously experience a learning experience. The listener becomes involved in imaginative or sympathetic participation in the experience of another with the very emotions that are involved.