When we communicate, how we say things is often just as important as what we say. And any good salesman (or poker player) will tell you that we often tell people a lot without speaking at all. Learning to interpret and send nonverbal cues turns a good communicator into a great one.
The same is true with the design of printed materials. Advertisements are designed to seek out attention and generate interest. Catalogs and leave-behind sales materials highlight what you have to offer in an appealing way. When it comes to internal correspondence, your team members deserve an attractive message just as much as your customers. The bottom line is that style can be just as important as content.