Why is SEO so valuable?

When people are looking to find goods, services, or companies they turn to google to find it, and by you being on the top of google searches; you are more than likely going to get found and be seen by people.  That is why SEO is valuable.  And best of all SEO is free (other than blood, sweat and tears, and knowledge).

Most importantly, SEO, is free advertising on google. And there is nothing  better than free advertising, right?