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.
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.
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.