The major search engines strive to find fresh, informative content to keep their users coming back. Blogs meet this need because they are updated on a regular basis, they are full of content relating to a particular or broad range of topics, and they are very search engine friendly.
Often times, your business blog will be found through the search engines before your actual website. Take any popular keyword and type it into Google. The majority of sites that appear at the top of the lists will be sites containing a wealth of information about that topic, not just sites selling similar products. Search engines are looking for content before anything else. Write good content on your blog, on a regular basis, and not only will search engines reward your work, but other people will link to your site naturally.