A poem must be remembered word for word or it loses its identity.
Jane Smiley, 13 Ways of Looking at the Novel
One of the movie cliches that I hate comes when one character quotes a line of poetry and then someone else, usually an attractive person of the other sex, either quotes the next line of the poem or names the poet and the title of the poem.
Does this ever happen in real life? Rarely. If you said, "I think that I shall never see," I might be able to respond with "A poem lovely as a tree." There are a few lines of poetry that a lot of people know. Yet few people today even read poetry, let alone remember much of it. The odds of two people both having memorized lines from the same obscure poem are astronomical, yet in movies it happens frequently.I am more accepting of those characters, such as Horace Rumpole in the old PBS series, who quote lines of poetry here and there when it seems to apply to the situation. It is much more likely that one person has memorized a poem than that two people, potential lovers, have done so.
Still, and this is what Jane Smiley seems to be getting at in the line quoted at the top of this post, lines of poetry are much more likely to be quoted word for word than lines from a novel. There are exceptions, such as the opening lines from Moby-Dick and A Tale of Two Cities, but you can paraphrase a novel with more ease than you can paraphrase a poem. Reader's Digest has never condensed a poem. You just can't do it or, as Smiley says, "it loses its identity."
Ray Bradbury's Fahrenheit 451 is remarkable in that, at the end, characters memorize entire books because the government is burning books. (Fahrenheit 451 is the temperature at which books burn.) A few people are said to have memorized the Bible, but generally speaking people never memorize books word for word. They are simply too long, and the language is rarely beautiful enough to merit memorization or repetition to other people.
Even jokes and folk tales are rarely repeated word for word.
Poetry, however, has power because it can be remembered word for word, and must be, even though few people do it anymore.