One custom that seems almost incredible to anyone from a prosaic culture like ours is poetic improvisation. However, cultures that valued poetry more highly than ours does have often cherished the ability to compose extemporaneous verse, sometimes considering it the defining mark of civilization.
The Gaelic cultures, for instance, all had bards, but the composition of poetry was not limited to the bards. Anyone with any claim to the slightest refinement was expected to be able to compose a verse on any topic on a moment's notice- even warriors in the heat of battle. Indeed, men were expected to be able to exchange off-the-cuff mocking verses with each other in the middle of a clan fight!
Virtually the exact same custom prevailed in Japan among the samurai, who were also expected to be able to compose improvised poetry. The Japanese even had the custom of poetry parties, where everyone would take turns adding lines to a group composition such as a tanka. This kind of poetry wasn't free verse, either- tanka were bound by strict rules of composition, governing the number of syllables per line and what references or puns should be made. Clever double meanings were especially prized.
Thinking back to such examples, it's hard to avoid the conclusion that we live in a barbaric society, where the most basic attainments of a civilized culture are all but unheard-of. Where other societies have expected virtually everyone to be poetically literate, we think of poetry as a much less than respectable way to spend your time. It's a sad state of affairs.