Why there is a need to write and marketing your articles through submit articles to various article directories?
There are baiscally five main reasons:

Free advertising:
When you write an article, you can add in links (using into resource box) that link back to your site. This creates a free advertising for your website. The article will also most likely be read by people interested in the topic of the article therefore people most likely to use the services which your business offers.

Viral Marketing:
You just need to post one article to a directory and that same article can start to appear on many other websites at the same time. This technology is called RSS (Really Simple Syndication). If you didn’t know yet, the power of RSS is simply wonderful. Big websites could potentially pick up and post your articles on their sites.

Some webmasters will pick up your articles and forward them to others, who forward them to others again. Soon, you could discover that your article has been published on hundreds of websites within days.

Boost Your Personal and Business Credibility:
Publishing your articles various article directories could potentially boosts your credibility and begins the trust cycle with your readership.

Bring traffic to your site:
By distributing your article all over the web you can bring traffic from all different kinds of areas. Imagine your article is about technology, but it ends up being posted on a business article directory and read executives who could potentially authorize the buying of your product by their company.

Generate Sales and Leads even without a site:
Even if you do not own a website, having an article online can act as your website. Just make sure your article is well written and doesn’t sound too commercial. Your article can be an example of your business and can include contact information like your email address allowing potential clients to reach you.