Oral tradition. Few things written down, long long stories all had to be memorized. The rhymes helped make it much easier to remember.

Storytelling culture continued after writing systems developed, but slowly died out. Poetry is basically a dead artform now days. Dylan Thomas died in the 1950s and Robert Frost died in 1963. I don't know of any masters who have come after them. Poetry died the same death that painting and sculpture died when classical art was eradicated by Jewish relativism.