In the worst case, they're lying.
In the best case, there's a communication breakdown.
Some possible communication breakdowns:
1) Identifying decision makers - It sometimes takes a while to find all the decision makers in an organization for an open position. It isn't always just the hiring manager and as a recruiter I'm not always told up front. Sometimes it might be embarrassing for the hiring manager, or maybe they don't even know. Sometimes the decision maker hands off a hiring assignment, but then sees its not what they want and takes back control. Unfortunately, that can sometimes mean a couple candidates getting deep into the hiring pipeline before it's clear. And then once you find the decision maker, that's when requirements can change where "remote ok" becomes "remote not ok".
2) Hiring ahead of the curve - Some clients will start a hiring process in anticipation of a new project coming through and then have to shut it down when it doesn't pan out. So it's possible a new remote team might be designed around a specific project and then the project gets modified or shut down and the remote team is no longer needed, but some candidates are funneled into other open positions that have different requirements.
3) Changing strategy - Some clients, especially startups, pivot in reaction to client or team feedback pretty quickly. If a job gets posted and candidates start moving through the pipeline, but the team keeps rejecting them, then the job req might change based on that feedback, but candidates already partially through the pipeline might feel like it's a bait and switch.
I'm sure there are more possible explanations, but those are a few I've experienced myself even though I'd consider myself a very ethical recruiter.
> I'm not sure what the compensation model for recruiters is
I charge 0 up front, 10% of the base salary on the start date and another 10% of the base salary on the 6mo anniversary if they're still employed.
Every recruiter is different though. Many charge an upfront fee or minimal hourly/weekly rate in addition to a % of the salary (or total comp).
> it seems to encourage bringing in as many candidates as possible over treating them with honesty and respect.
Those recruiters don't last very long. And it's a sign that they don't know what they're doing. At that point they're glorified paper pushers, shuttling resumes from one place to another.
If I don't have someone specific in mind for a role, then I typically review up to 150-300 resumes for a given position and reach out to 50-100 for pre-screening questions. Of those, only about 25-50 might respond. Of those, I might interview 10-20. Of those, I typically recommend the top 2-4 candidates to my client. I don't wait to pick the top 2-4, I just know from running my own company and engineering teams who I would hire and who I wouldn't and recommend candidates as soon as they successfully cross all of my screening steps.
The problem is if you flood a company with candidates, it takes them too long to schedule all those interviews and make a decision. By sending only 2-4, I can get them all through 2-3 rounds of company interviews in 1-2 weeks, and then the company can make a quick decision.