The author most likely uses this structure in order to emphasize a word or a phrase. By following this structure, the author imitates the sentiments of the speaker. The speaker describes a fun, desirable situation when he talks about what the hallway looks like. This sentiment contains more words. However, as the poem progresses, we get closer and closer to the feelings of the author. The number of words reduces as well. This highlights the loneliness of the author, and culminates in a single word: "lonely."
