There are lots of good reasons to use a graphic/web designer for your design needs, but there's ultimately two major reasons to hire a designer; Time and Money.
Regardless of the size of your business, your time and focus is better spent on your work. Giving a designer your business' design needs frees you from having to spend your precious, and likely already limited, time away from other projects that require your attention. The designer will know which programs to use and how to use them in order to create your logo, website, or whatever your project may be in a timely manner.
As for saving money, it's a common idea that if you do something yourself you'll probably save a lot of money, but in the long run you'll be glad you hired a designer instead! Botched design projects, especially print projects, can get costly very fast. Incorrect layouts, images with too small or too large a resolution, generic/free clip-art, printing with too many colors, or even using a "cheap" designer can all become costly and overwhelming issues for inexperienced designers and "do-it-yourself"ers. A quality designer will not only already know how to avoid many of these issues, but they will also provide you with all of the final files in every color, size and format you could possibly need so you won't waste time OR money getting your project done. Not to mention that having a high quality, unique design for yourself and your business gives you an edge over your competition.
So, feel free to take a look at my portfolio of work using the links above, and request a quote for your project today! I provide a large variety of design services, both for professional use (business cards, websites, logos, etc) as well as personal use (t-shirt designs, image manipulation, tattoo designs, etc).