One reason is that you want people to find you. Being as that there are millions of web pages you have to stand out and understanding SEO is very important you the success of a business. Choose the right keywords or keyword phrase, think outside of yourself as to what a person might type in to find your business. Look at similar web pages to get an idea of what they use.
Another is that you can track your marketing results scientifically. You can research how your site is searched and make adjustments as needed to find the best possible design that gets you the most traffic.
