People in the
SEO business who act like this are merely carnival workers, hawking their booths to the midway. Unfortunately, the web is still a place where these folks can run around from town to town, virtually speaking, staying just ahead of the cyber-cops.
Of course there ARE legit web marketing companies who do search engine optimization
SEO work. You can tell who they are by one essential fact... they make absolutely NO guarantees about results. They tell you what they are doing, everything they are doing and that is their marketing strategy to you. Some of them actually operate web-sites where they openly publish the how-to and tutorial techniques. They have no secrets.
So, why would you hire someone who tells you there is no magic trick that guarantees success, and merely charges for their time to apply commonly understood, proven (relatively of course) web design and
SEO technologies? Why?
Because they may be able to do a more complete, and faster job of this work than you could. They have more experience, etc.
But, given enough time, with enough reading and research, you could do about as good as most
SEO firms. Problem is, do you have the time and energy to devote to this? It may take months or years for you to (1) discover what is needed, what techniques actually work, and (2) then do the work.
That's what drives the success of legitimate
SEO companies. They don't hide anything. They aren't magicians. They're just workers in the vineyard.
And, workers who actually get something done will always have a job, even on the 'net.