Why pay for traffic in search engines' paid listings, if you can achieve high organic rank - the gift that keeps on giving with traffic, leads, and sales?
First, to digress a bit and to speak to an area near and dear to our hearts, high organic rank isn't really free anymore.
With more and more business turning to online marketing, and in large part to search engine marketing, the competition for the first few listings of the search engine results is only growing. The sites ranking at the top of the results for competitive terms are paying in some way - either directly paying a search engine optimization/marketing company or paying with their own time and resources.
See our blog post "Search Engine Optimization: Not As Exciting As Magic" for much more on this topic.
But, now on to our main point:
Why would you need paid search advertising once you've achieved high organic search engine rank?