When we walk into a bookstore to select a new book to read, one of the first things we do is look at the cover. IF the cover LOOKS enticing, we might take the time to pick the book up off the shelf and take a quick flip through the pages. IF the pages LOOK decent, THEN we might read the blurb. Visual presentation is a KEY to good writing.
I find that getting kids to pay attention to what their writing looks like helps to motivate them as writers. A lot of kids appeal to their visual senses, and this is a way to get them to do it in their writing. We spend a lot of time looking at different book covers and discussing what works and what doesn't. We also compare different covers of the same book. Then the kids take what they have learned and apply it to their own published pieces.