SEO is Google’s way of determining which sites deserve to rank highly for each query entered into its search engine. Without modern SEO, it would be extremely simple to manipulate the search results so that the site with the most links or the most pages—all easily generated by software—consistently ranked #1.
SEO is important because it keeps the search results fair. It reduces the ability to manipulate these results as much as possible, so that the sites appearing for each search are there because they deserve to be there. Hard work and a website that appeals to visitors correlate with high search engine rankings, so if your site meets these criteria, you’ll have a better chance at showing up in the results.