SEO is mostly cleaning up after lazy developers or WYSWIG site builders who didn't write standards compliant, accessible, lean code and didn't know anything about information architecture. I know because I do it every day.

Search is how most people find most things online, period. Designing a website with such a contempt for SEO is a recipe for disaster. Yes, some websites don't need SEO or SEM, because they're naturally viral or sticky. Some products also don't need any marketing to catch on. In both cases, this is the exception and not the rule.

(SEO is also spending a large amount of your time defending your reputation against something that was left behind for you by snake-oil salesmen.)