I'm really surprised that so many employers use the middle man to find contractors. How do you tap into that market and skip the middle man? Seems like a win-win to me. (Except for the recruiter who's left out in the cold)
Of course, in the world of sales, those relationships can form quickly. Even if you've never heard of me and my staffing firm, I can present you tickets to a concert or golf tournament, or something similar, and win (buy) favor fairly easily.
Most of these middleman staffing firms are not really differentiated from one another. They find a client and leech on to it.