The reason is that a putting up a website doesn't mean your going to get visitors. It's what you do before you put the site up and what you do after you put the site up that counts. Websites and software tools don't make money....YOU DO!
SEO is not hard to learn and it is a process if you want your site to get more visitor and to have more sales. Keep researching and join in the forum so as to get more information.Or you may read this site http://googlerankings.com/basic.php
SEO is a continuing learning process. So if you want to learn SEO it takes a lot of hardwork and patience for the time that you will consume. New tricks can come up in the years to come and it is for us to discover them.
SEO is easy its the implementation of SEo thats a b14tch
couldn't have said it better.
Plus the time it often takes to see results makes you wonder if you're work is worth it. Then 6 months later you suddenly rank well for a term you haven't worked on in months....