As stated here on Search Engine Land, a website author benefits from confirming his Google authorship with Google. When you click on the back button after reading a blog post from a particular author, the visitor will see a maximum of 3 links with “more articles from …”. The condition for seeing this link is that one must have read the blog post for a certain amount of time (about 2 minutes). For example, Google knows that the blog post is interesting for the reader and will therefore want to show more related search results.
UPDATE 14-01-2015: Google Authorship images are no longer shown in Google
When you see more links in the search results, you will get more clicks and visitors to your site. Clicking on links of a particular author is also a sign that people are satisfied with the articles of this author and that contributes to the so-called Author Rank.