The subtly of non-fiction is built on grammar. Irony and satire are grammatical conventions. We see them when we see the grammar. Authors are spoken about as one who can turn a phrase, that's grammar. The art of persuasion is grammatical.
Authors revel in grammar when they write.
Teachers use grammar when analyzing literature. They show patterns, that is grammar. Readers can follow arguments that are well written because of the grammar. Parallelism is an important writing tool because it provides reader clarity. The reader needs parallelism to interpret.