I use it, I advise on it, but many don't get the need for it or its meaning.
Search Engine Optimization is all about getting web sites noticed, and ranking well in search results. Above all, it is about writing clear, cogent, relevant textual content. It is not about repetitive "spam", hidden phrases, flashy appearance and irrelevant links.
These two links from Jill Whalen, a leading practitioner, help explain well.
Back to SEO Basics With Keyword Research
Back to SEO Basics: Choosing Keyword Phrases