I'm a software engineer that is currently bootstrapping my technical recruiting business. Companies say they like working with me because:
1) my candidates are experienced (I do the vetting and they are all a part of my network which I continue to build every day)
2) I spend a lot time finding what a candidate wants and what companies want (so far 80% rate of engineers getting offers when I match albeit low sample size)
3) I don't spam (candidates or companies- generally only make 1-2 matches per company per month)
The reason so many bad recruiters exist is because the contingency payment model really makes it so that spamming seems beneficial in the short-term and makes the whole recruiting game very transactional (see real estate agents). And contingency agreements are much easier to get (vs retained search).
I'm working on finding more creative ways to align incentives better and building better sourcing tools.