Ask HN: Why do only some YC companies recruit on HN?
Why does the same small set of YC companies regularly submit hiring posts on hacker news?
In my model of the world it's either a good recruiting channel (in which case most or all companies should do it), or it's not. What am I missing?
Because most YC companies aren't growing. They are dying a slow death by being a zombie company.
Presumably the OP was asking about YC companies that are growing and hiring. The majority of those don't take advantage of HN job ads, and the question is why.
We need to do a better job of making this option better-known to YC startups. It tends to fall through the cracks on both the HN side and the YC side because everyone's busier with other things.
See the FAQ "Can I post a job ad?", it's a sort of ad reserved to YC companies. https://news.ycombinator.com/newsfaq.html