Let's begin with what we know or can confidently surmise:
- Every culture developed both poetry and song long before the ability to record either.
- Before the written word, at least, what distinguished poetry and song from what we now call "prose" was that verse was memorized, performed and preserved word-for-word.
- When literacy was developed the convenience of text tilted the balance in favor of poetry. That is, before 1920 people could recite more contemporary poems than contemporary lyrics.
- Poetry's advantage was nullified when, due to radio, music became at least as easy to disseminate as poetry.
- The cross-cultural decline in poetry's popularity since the 1920s has been neither universal nor uniform. By far the hardest hit has been anglophone popular culture, from which contemporary poetry has disappeared.
The sky hasn't fallen. Indeed, this disappearance has gone largely unnoticed. Out of sight, out of mind. (Indeed, when that expression was translated literally into Russian and back into English the result was "invisible idiots"; that's not a bad description of how poets are regarded today!) Society seems to have survived quite well without poetry. For the sake of this discussion, though, let's assume that poetry could matter and that our culture would benefit from absorbing more of it. Rather than complain about the lack of iconic contemporary verse or sing silly choruses of "Yes, we have no watermelons" let's consider the question:
"How can poetry compete with song?"