The vast majority of website visits happen because of the results that show on a search engine. As Ken mentions above, 60% of the clicks go to the top placed site, so having a high ranking site will create more visitors to your site and hopefully more business for your company.
However, this will only really work if the site itself is ready and users find what they want on arrival, so
SEO is not just about high rankings, it is also about on-site optimisation.