I can't say anything about YC specifically, but, anecdotally from working at a great place that was fairly well known and that constantly had job calls going ou

I can't say anything about YC specifically, but, anecdotally from working at a great place that was fairly well known and that constantly had job calls going out for months to years on end, it's because the bulk of people applying actually sucked at either software engineering or at not being weirdly aggressively rude or both. You might think that the people on HN are all super brilliant engineers with patience and social grace in spades, but I doubt it.