Well I believe that every day a webmaster is to some extent usign SEO on his site, just different methods and perceptions of such. For example i am always looking for links and advertising and a quick buck towards getting more hits per day. But on the other side of SEO, the HTML itself, I dont really do much as long as you include METAs, <H1> <H2> tags and <title> then if the content is good you will reep the benefit from the search engines and the users trying to find their information.
For example my site www.wiiroom.net has never been submitted to search engines, I let them find me, imo thats the best way to go. I have though submitted to over 250 directories, of which 146 links are established to get backlinks and hopefully a decent PR update next time.
Half of my traffic now comes from google, as it found this page:
http://www.wiiroom.net/forum/showthread.php?tid=20
about the wii shipments in 2007, and all of a sudden my uniques went through the roof! as you can see by the pageviews on that particular page.

If you have content + links SE will find you
Alex