Why? HN users tend to have income, and probably spend money on work/productivity related products. Example ads: hosting, programming tools, job boards, vc/legal services, startup services, etc.
Anecdotally, I'm not sure I've ever clicked an online ad intentionally. If I have, it was during the 90s.
Anecdotally, I click on relevant ads or ads that interest me all the time.
I think what GP means is that the crowd on this website are savvy and will just ignore the ads.
I'm not sure about that. I mean, this whole place is inadvertently an advertisement for the Ycombinator program. And people click the YC company job ads all the time too.