Benefits:

Getting inbound links or back links in amount and value can weight your search engine rank enormously.
Increasing traffic of your website and getting noticed by search engines take more time and endeavor.
Get your website listed in major search engines with directory submission.
Directory submissions assist in increasing the popularity of your links.
Branding is similar to keyword targeting in that it improves overall awareness of your business.
Keywords: Using keywords that are part of your text for your directory improves the keyword relevancy that you use in the website title during the directory submission.
Importance:

When submitting to a directory, the major impediment as well as the major advantage lies in the human editor. Your submission will be analyzed by an actual person who decides how relevant and exclusive your website is. After transient his scrutiny and editing, your website will be acknowledged in the directory. This automatically establishes the reliability of your website; hence search engines will think links submitted to directories.

Note how vital listing in a directory is. If your website is near to the ground on content but rich in images, flash content, etc. search engines may not be capable to categorize your website when the search spider visits your site. By submitting to a directory below a particular category, you allow the search engine to classify your site below a related topic.

To boost visibility online is the central part of every online business marketing strategy.