Why Would you need Search Engine Optimization (SEO) for your site?

SEO is the process of structuring a website, so that is easily found and indexed by search engines, thus making it more attractive to your visitors.

SEO is the easiest, and most affordable way to advertise your site

This method is free of any risk, in many cases paid advertising is subject to click fraud risk: your ads are getting clicked by softwares thousands of times, without any real profit to your site. High-tech pay-for-performance programs (such as Google AdWords) claim to have advanced protection against such behavior (and they do have), however the risk can never be reduced to zero.

SEO is a long term investment

If you have a pay per click or other paid online marketing, then as soon as you can`t afford to pay the advertisers anymore, the traffic to your site will drop.
Although implementing a good SEO will probably cost you more than a pay per click campaign, for example, you usually only pay this once. Once you have good rankings with SEO, these will last longer than the traffic generated by any other kind of advertising.

Finally, a site with a proper Search Engine Optimization looks professionnal, it is easy to browse, and will always place you at a better ranking than a site wihout SEO.