It's a bit like ProductHunt. The only people that look at ProductHunt, are the people that post on ProductHunt—or at least that's its reputation. Though that's an unfair comparison, because I think on HN there is actually genuine engagement by other builders (or perhaps I'm mistaken about PH).
Not quite as bad, but I do think the ShowHN posts suffer a form of the same issue where most posts seem to get very little attention and the little there is, probably comes from other people who post to it, rather than receiving the attention of the wider community (which, at least HN has).