The answer is simple - every website owner. Whether you operate your site for hobby or profit, you want your site to be popular, and SEO is one of the best means of achieving this end. In terms of business, SEO will increase traffic to your site and everything that comes with it - greater popularity and brand visibility, conversion from casual visitors to active customers, and ultimately higher sales volume. No less important, quality site optimization will enhance users' experience of your site through efficient navigation and shorter page loading time.