All written communications convey a meta message; that is, they broadcast a message that is separate from the literal meaning of the words you use. If your writing is clear, well-organized and accurate, your readers will tend to assume you are competent, conscientious and reliable.
If your writing is badly organized, trite, and full of errors, however, your customers may unconsciously assume your products and services are below par or that you lack the skills to handle the job. At the very least, they will question your lack of attention to detail.
In other words, written communications affect your company