Why is Journalism a Profession?

In Bernard Lunn's recent article, Journalism 2.0: Don't Throw Out the Baby, he described bloggers as "passionate experts first and journalists second."

Lunn then goes on to list the aspects of journalism that he deems important, including a desire for truth, humility, skepticism and independence from commercial interests. His list echoes concepts expressed in the Pew Research Center's Principles of Journalism.

Why aren't journalism principles, which are essentially synonymous with critical thinking, being imbibed by our culture and education system already?

Lunn describes an expert that thinks critically. This implies that experts are qualified to be journalists, i.e., authoritative bloggers. Of course, these experts may have to adjust their presentation to accommodate differences in audiences. Still, experts must apply the same, if not a greater degree of critical thinking as journalists, otherwise they would not be experts.

Which forces me to ask: why is journalism a profession?