Usage. The ancients liked to use the best lines from the poems of previous generations of poets, which is the inheritance and development of poetry. It also increases the ambiguity of the poetry itself, making people feel profound but not rash and explicit.
First of all, this is an allusion to Tao Yuanming's use of Chu Ci in "Peach Blossom Spring". In "Li Sao" by Qu Yuan, a poet of the Warring States Period, there is a line: "Drink the dew from the magnolia in the morning, and eat the fallen chrysanthemums from the autumn chrysanthemums in the morning." (In the morning I drank the dew on the magnolia, and at night I used the remaining petals of the chrysanthemums to satisfy my hunger.) Tao Yuanming used this way, and the readers Not only do you see the Peach Blossom Spring with "delicious grass and colorful fallen flowers", but you also think of Qu Yuan, which opens up the context of the poem and leaves you with much more room for aftertaste.
In addition, there are too many "falling flowers" in ancient poetry. Although they are beautiful, they are aesthetically exhausting. It will feel ordinary when you read it, but Luoying is beautiful and novel.
Of course, Tao Yuanming and Qu Yuan were relatively early poets, so the customary expression of "falling flowers" may not have been formed at that time. Because ancient Chinese is dominated by monosyllabic words, unlike modern Chinese. So Qu Yuan and Tao Yuanming both used Luoying.