Your traditional website is static, meaning the content doesn’t change regularly, while a blog, which is an instant self publishing tool, can be updated, added to and changed much more frequently. Having new content on your site increases visits to your site by the search engine spiders.
Additionally, each time you create a post to your blog, you are adding a page to the site as far as the search engine goes. Right now this site, Syndicating Your Content, has close to 400 pages. You can see how easily you can build a robust site with a WordPress blog.