Nina Kang suggests that contemporary verse is simply difficult to remember:
Unfortunately, that strict meter we dislike was a pretty valuable mnemonic tool. Memory is reconstruction, and when we recite, we must reconstruct from the pattern of rhyme, internal rhyme, and meter, and from the remembered sensations of our throat muscles articulating the phonemes. During the era of rote memorization, poets generally used predictable and memorable formal techniques where “rhymes hinted at their partners and sense—and small remembered groups of words – contributed enough to restore the whole … as satisfying as solving a crossword clue” (from “Gray on a White Night: Reconstructing the Elegy through the Small Hours” in the London Times of April 22, 1960, according to Heart Beats). As a result, memorizing free verse poetry often feels like solving a crossword with only half the clues.