Search engine optimization, or SEO as those in the industry call it, is largely an unknown term to those who don't work with it. In fact, most people have never even heard of SEO. It is telling that even within the SEO field, not everyone agrees on how it is best achieved.
There are some standard guidelines like high volume of content on the website, giving outbound links and receiving inbound links, properly formatted meta tags, and a well organized site. Most in the industry do agree that these are basic tenets for a successful SEO program, but there is no magic path to getting there. SEO is not divined from a scientific method, but remains almost like a dance, an art form. The SEO provider is constantly working and reworking their formulas while they keep a close eye on the website's movement in the rankings.
Most professional SEO providers will provide their client a level of detailed in-depth report similar to one another. But that's where much of the similarity ends. While most will not have any outright conflicting advise, their content and their approach will be different. If you polled 10 providers for reports, you'd likely get 10 different versions.
The industry is an exciting one for SEO providers. Because there's no clear cut right or wrong way, much of their work is based on inherent knowledge, experience, and a whole lot of intuitiveness. Nobody has a secret plan that will work 100% every time, and every website is different in its needs and goals. Building traffic and improving rankings are the only way a SEO provider gets a "report card". And because SEO work takes time before the effects are seen, there's almost a magical excitement present that the suspense of not knowing brings.
Because things are changing so quickly with search engines these days, it takes a professional SEO organization to keep up with where things are going. For an individual to jump into doing SEO work on his own site would require a lot of time, and a lot of faith, and an extensive undestanding of SEO. There's a reason that some professionals have a great track record and others don't. It takes experience that can only be gained through a large client base.