Suppose you think the average article in The Economist is terrible. One might then conclude that it's not worth reading in general. But HN acts as a recommendation, and that might be a strong enough signal to interest you in reading this particular article.
But The Economist has an unfriendly layout or puts up a paywall or blares ads at you, so you flip into reader mode as soon as you see the article. You retain an impression that The Economist is terrible, while still reading this article.
