because technical recruiters, contrary to popular belief, are not hired to get the best candidates.
Technical recruiters (and agencies) are hired to give the middle manager denyability if a hiring mistake is made. I mean, if you hire your brother's friend and he turns out to be some kind of crack fiend who ebays your spare parts bin for more drugs, well, you've got a fairly good chance of getting fired in the fallout. Now, if a recruiter recommends the same guy and the same thing happens, well, now you can push some of the blame off on the recruiter. there's no question about nepotism, etc.. the professional recruiter recommended the guy.