Schools and the legacy of Leavis encourage the idea that poetry teaches us something about life. Poetry traditionally is treated with tolerance and reverance, and thought of as a vehicle for eternal truths and deep emotion, so some people cast their opinions into poetry to make their thoughts deep and eternal. Populists and propagandists, knowing that people are more gullible to poetry than to prose (and more gullible still if it's set to music), cast their message in an overtly traditional poetical form or use overly poetic phrases, hoping to cash in on poetry's heritage and bask in the aura of the greats.
But it's not only Lady Diana-lovers who do this. Good writers too know that calling one's short prose poetry is a useful (sometimes the only) way to get it read. As well as gaining respect by categorical association with past works, a poem offers the writer many ways to make the reader believe that the poem is significant - e.g.
The above list of ploys includes features that some have described as defining characteristics of poetry -
Poetry seems rich in such facilities, which is perhaps why readers often think a poem deep but can't say why. As so often, evolution may provide an explanation.
The human brain is an amazing organ, one that's developed through evolution from being able to clobber mammoths to knocking off sonnets. However, evolution never does any more than necessary. As sight evolved, there was no survival advantage in being able to deal with situations that didn't happen in real life - our eyes might be able to help us distinguish friend from foe at a hundred yards, but they're easily tricked by optical illusions. Thought and language processing is even more complex than visual processing, so perhaps it's not surprising that poetry can create an illusion of depth and meaning by short-circuiting the normal routes (much as stereograms give the effect of depth though they have none), exploiting a loop-hole that evolution has left open. As with stereograms, surface obscurity may be necessary to produce the effect, and there's a lot of skill involved in producing an effective illusion. Indeed, I'd say that not merely skill is involved; it's an art.
The intelligent layman no longer looks to poetry for insights into our times. The only surprise is how poets got away with it for so long. Yeats' "Easter 1916" and Eliot's "The Wasteland" may have summed up a generation's hopes and fears, but that was long ago. The game's up now. Even poets admit that poetry's explicit statements aren't always to be taken at face value. TS Eliot said that "The chief use of the 'meaning' of a poem, in the ordinary sense, may be ... to satisfy one habit of the reader, to keep his mind diverted and quiet, while the poem does its work upon him."
There's still much of interest in poetry but we shouldn't kid ourselves that poetry will solve our problems or have anything to say about the human condition; it says more about human conditioning. Something that provokes feelings of profundity needn't be profound. The modern lyric simply doesn't have sufficient width to support such depth. Let's leave profundity to prose.