At the end of the day, a recruiter needs to have the blessing of the employer even if the employee is paying. If employers will not speak to the recruiter, he cannot get jobs for his customers, and he will quickly lose customers and reputation.
'Reverse Recruiting' doesn't make much business sense.
The Recruiting Gig
So what do recruiters actually do?
A company has an open position. If they just invite resumes, they will get the equivalent of the C+ student with no extra-curriculars who applies to Harvard (you know, just in case). Unlike Harvard they don't charge to file an application, which just aggravates the problem. They don't want to charge, because then truly qualified candidates will resent having to pay since it implies the company is doing them a favor by reading their resume, and will just find another job.
So they hire recruiters to refine the pool of applicants. Recruiters are working with dozens of companies to do the filtering, so an unqualified candidate for one position isn't necessarily a total loss for the recruiter if they can find another open position that the candidate may be good for.
Let's say I want to work at Ford, Chrysler, or General Motors. None of them are actively recruiting me. I have applied to the jobs on their website with no luck. I have talked to recruiters to see if they have any jobs in one of those companies, but haven't had success there either.
What would a reverse recruiter do in this situation?
If I am not qualified, taking my money to send my resume to those companies will only serve to make the companies pissed off at the reverse recruiter. After all, they didn't want me when I applied the first time, and now this reverse recruiter is bothering them with me again. This means the reverse recruiter has not only failed his client, but he's also pissed off three companies who will likely not consider any potential candidates he approaches them about (or even answer his calls/e-mails).
If I am qualified, then I would have already gotten the job through the existing system. Either they would have looked at the resume I submitted and sent me a reply, or if I was filtered by a stupid computer system, the recruiters would probably have info about the opening and be more than happy to pass along my resume (and fix whatever error got me excluded in the first place). If I had still somehow slipped through, what would make the reverse recruiter any different from a normal recruiter (other than the fact that he is getting paid by me instead of the company?).
In order to make this line of business even worth considering, a reverse recruiter would have to charge more to the clients than a business would pay to fill the position, since the chance of success is smaller. And who will use these reverse recruiters? The most likely would be unqualified people desperate for a job -- the people least likely to even be considered by companies in the first place.
So it doesn't make much business sense to be a 100% reverse recruiter.
What makes things worse is that unlisted position openings are often filled by networking (like bonuses to employees who find an opening for a position). So the reverse recruiter is competing with people who are already involved with the companies, and who have the natural filter of friendship working for them in finding qualified candidates.
The closest thing to a real reverse recruiter would be a career counselor. Someone who you go to who helps brush up your resume, look for job openings, and give you advice on how to appeal to each company (and perhaps even put you in contact with someone there).