The majority of search engine users are more likely to choose one of the top 5 suggestions in the results page so to take advantage of this and gain visitors to your web site or customers to your on-line store you need to rank as higher as possible.
SEO is not only about search engines but good SEO practices improve the user experience and usability of a web site.
User’s trust search engines and having a presence in the top positions for the keywords the user is searching increases the web site’s trust. SEO is also good for the social promotion of your web site. People who find your web site by searching Google or Yahoo are more likely to promote it on Facebook, Twitter, Google+ or other social media channels.