1) RSS and feed readers make it easy for readers to subscribe to every post you write, and be notified the moment you publish it.

2) Many people who read blogs also write them, and many of them have hundreds or thousands of subscribers. If a few reputable bloggers syndicate your story it can have a cascading effect where many of their readers share your story.

3) Popular blogs that solicit reader feedback may have dozens or hundreds of comments on each post, adding unique content which the page can rank for.

4) Optimizing a blog is more about capturing attention and getting credit for spreading ideas than it is about optimizing page copy to match search relevancy algorithms.