If Search Engine Optimization is so important, why didn't it get done when my website was originally designed?

In most of the cases, site designers are highly skilled and creative people who see their job as putting your ideas (or their ideas) on the web. More often than not, these designers have not received any training in search engine optimization and don't even think about it while developing your website design. In addition, search engines are constantly changing their ranking criteria. Often, website designers are not fully up to date with changes at search engines.