I'm guessing with near certainty that you're talking about contingency recruiters. Contingency recruiters are the type you "pay for performance" -- if you hire someone, they get a fee, typically ~20% of first year's salary. If you don't, they get nothing.

In theory, this business model incentivizes everyone perfectly -- they only get paid if they perform. In practice, it's awful and doesn't work at all.

To understand why, think about it from their perspective as an honest recruiter trying to do a good job. You give them a call, and have all kinds of very specific requirements for the kinds of candidates you are looking for. They need to spend a lot of time upfront working for you, which is an asymmetric commitment, since you aren't paying them anything until they hire someone, which means a few weeks of free work on their end up front in the best case scenario. Just like there are a bunch of flaky recruiters that drive by and waste your time, there are a bunch of flaky companies that do the same to them, except they don't have any upfront commitment.

What this means is that the contingency recruiter model tends towards a resume dump. It's nearly completely worthless -- the only thing you could get out of it is to insist that they just send you a dump of all resumes they have that match your criteria.

The good news is, there are other recruiting models that work much better.

A retained search is usually done for a more senior position, and it works very well. You agree that they have the exclusive on the search, and agree on some large fee you will pay them for finding you a VP of X. You pay half of it up front and you won't get it back if you don't end up hiring someone -- the reason is because they will dive deep into your needs and go out and find candidates specifically for you. They put in a lot of work up front, so you pay some up front, too. They will often have great relationships with the candidate pool you are looking for, and might even place the same person 2 or 3 times throughout their career. Because there more risk up front for you, you will interview their references extensively and rely on their reputation.

The third type of recruiting business model that works really well is a contract recruiter. This is someone who is basically a contractor for you. They may work full time, or maybe 1/2 to 1/3 of their time at several companies, depending on how many positions you are trying to fill. You pay them a flat rate for their time, and will likely set performance expectations (for example, it might be reasonable for one 1/2 time recruiter to hire 1 great engineer per month), but their pay will be fixed and not performance based. This person comes into your office, becomes a part of your team, understands exactly what it is you are looking for, and helps with all of the leg work of recruiting: sourcing, screening, scheduling, extending the offer, and onboarding. You take some risk, because they might not be very good and you might not find that out for a few months, but no more risk than you take with any other regular employee. If they are good, this person will become a very critical part of your team, and will help you build an amazing team!

There are a lot of people that have tried to solve the contract recruiting model, and most have failed. The only people I know doing well are Triplebyte, and I hope they succeed because, as this thread shows, there are a lot of people who would like it to work!