It would be more precise to say that Quora is for questions and HN isn't really. HN is a link site with an "Ask" feature tacked on. "Ask HN" posts are actually

It would be more precise to say that Quora is for questions and HN isn't really. HN is a link site with an "Ask" feature tacked on. "Ask HN" posts are actually penalized in the overall rankings, so it's relatively hard for them to get seen by many people. That's not to say that they're unwelcome, but it's just not a conducive environment for many questions. Quora, on the other hand, is a question and answer site. Q&A is their bread and butter. That's what people go there for.