I go to HN because it isn't just a random news site with laypeople commenting on tech they don't understand; it's an aggregated news site with commentary from the exact people I want that commentary from. I've found myself not bothering to ask questions I want to ask because no one will see it after a certain amount of time despite the fact that threads that are over a year old end up on the front page.
Additionally, it sucks having to click two times (User > Comments) just to see if someone's responded every few minutes/hours. I've got better things to do. Notifications are a passive feature; you can choose to ignore them or turn them off, but I think they are vital to sites that tout their userbase and the intelligence therein. You could almost say Reddit's success can be hinged on the orangereds.