Unicorn hunting is probably some of it. I followed up on one that sent me a rejection letter after two interviews and just said "I see your job has been re-posted" Never heard back. =)
I both got a job through such a thread, and have now seen the other side of the applicant pipeline. The average applicant (in general, idk about HN in particular) is not very strong! Especially true when you consider the alternative of preserving runway and being patient.
Anecdotal data
As a hiring a manager, I posted a job offer in Who’s hiring, and doubt I’ll do it again anytime soon.
In my field of work, I am looking for skills other than software (maths, physics, engineering…). There were few qualified applicants coming from the thread. Most of them were nice. One candidate, whose background was unrelated to my field of work, got very offended when I told them it wasn’t the right fit.
This never happened when screening candidates that reached out other means (LinkedIn, Lever…)
There's a large number of people who might have the skill. Tech companies have been laying people off, too, which increases the talent pool. That lets them be picky. If patient, they'll get a better employee.
On the other side, techniques recruiting is getting harder. They've long had to deal with applications that have nothing to do with the job, by people with no experience, and people who can't code. Now, AI's might be writing applications or sample code. On busy sites like HN, they might also just get many applications. Even a reasonable, hiring manager might have difficulty trusting an application enough for an interview.
Those are my two theories for most of it. Others include companies prioritizing culture fit, status, or job adds that are schemes. Some of these happen in other places.
My workplace reposts the same senior dev ad each month. And we’re not reposting it because no one was good enough last month, it’s is we want all the senior devs, we’ve hired a few from there now.
Some of the posters even ask you to contact them directly, and then ghost you when you respond.
It probably varies from company to company.
Sometimes the company might set the bar impossibly high. Other companies might be rejected by the candidates.
Given the current economic situation, I think a tech job that stays open for longer then 2-3 months is a warning sign about the company. (Except for jobs that require ultra-rare skills, but most jobs I see don't require them.)
Some times they get so many (often low-quality) applicants they just bin hundreds at a time for arbitrary reasons.
Other times the jobs were never real, it's a "growth hack" like other forms of spamming, posted to advertise the company and sell the illusion the company is growing, not slowly sinking.
I am on the site because it is full of very thoughtful and intelligent people in the tech industry.
I don't stand a chance in an interview pool made up of a sample of HN readers.
Outside of HN, I am a successful IT director, with a graduate degree and a good career. Here, I am an auto-reject bottom-rung parasitic loser that never went to Stanford.
I got a gig from who's hiring a few years ago. I also interviewed at some other places which were not a fit. Some places never got back to me. It has been a mix.
I've seen the same position posted for a YC-backed company for over a year. I commented on it months ago, it's funny to see this topic come up again. We seriously need some legislation in this area. Finding a job as a tech worker is hard enough.
Tech industry hiring heavily believes in the "fixed mindset." Meaning that people are unable to grow. Combine with extreme risk avoidance, an explosion in the number of stacks, and no appetite for waiting a week for a dev to learn another thing. No hire.
Hard to prove and I don't want to accuse anyone, but could be just posting for visibility.
People are searching for people. I'm not in the demo. yet it's interesting to look where the interests are.
And if you look further there are enough of people who were actually hired because of this.
Collecting resumes then upselling you on a service.
Technical and culture fit likely.
Though with a large pool you’d expect it to close.
Hope they are real jobs.
I've posted on "Who's hiring" for years now, and hired many engineers from those posts. We reject the vast majority of candidates, and to those who we reject, it might seem like we can't hire "a single candidate." That's not true - if it were, I'd stop posting here!