Because these three distinctive words are the essence of this poem, expressing the changes of the times and the fall of the dynasty. Using so many identical words but only three different words, he can still express such deep emotions, which shows the poet's superb ability.
This poem is "Guo Feng·Wang Feng·Mill Li" in "The Book of Songs". This poem has three paragraphs, each paragraph is almost repeated, and only one word in each paragraph is different. In fact, this poem uses the changes in crops at that time to express the image of a wanderer whose home and country are broken. Although there are only 39 words in the whole text and 36 words are repeated and only three words are different, the emotions to be expressed in this poem are vividly interpreted.
In fact, this poem cannot be called perfunctory. I think it was done deliberately by the poet. He just wants to express emotions that are not "perfunctory" in a seemingly "perfunctory" way. These three words are progressive, and they lead the emotions of our readers. From a small crop, we can experience the image of a wanderer who is homeless and the country is in war. I think it is this seemingly strange format that draws our descendants to pay attention to this poem.
In fact, the format of this poem is the key to us future generations remembering it. Ancient poetry actually uses simple language to express complex thoughts, and this poet uses a seemingly simple way to convey complex emotions to us. I think this poem is not "perfunctory". This poem reflects the poet's superb ability. He can express such rich emotions through the transformation and progression of three words. Shouldn't we admire him?
I think most of us still like this poem very much and admire the poet, because this "perfunctory" part is exactly what we admire.