When LinkedIn made a push a few months ago to take over the job boards and the recruitment industry, as the CEO of an executive search firm, I confess I was intimidated. However, while at first it seemed to many people that social media was the new online job board; the shine wore off quicker than some of us had feared.
Not everybody on social media is looking for a job, but everybody is "looking for a job." While nearly every LinkedIn profile suggests that the individual is open to career change, very few of the people behind those profiles are serious about it. Therefore, for any hiring manager or recruiter, it takes a significant amount of time to simply find someone who is serious about moving jobs rather than just willing to speak about the position to gain further information.
Many of these individuals don't seem to have resumes put together either, therefore to present them to clients means either giving a "snapshot" of the individual or waiting weeks for the potential candidate to finish the resume (if they do). The job boards have resumes there and available, which (most of the time) translates to the job seeker being interested in making a move.