The words an author uses are important because they're meant to get a reader's attention, in some cases. They're meant to draw you in, and have you clinging on every word, wanting more. In other cases, the words and author uses is meant to inform the reader, telling them about a specific topic, informing them about things they have misunderstood. And other times they're meant to change the reader's mind, to show them why one thing is better then the others.