Why? On average I found Digg's slice of news (current events + comedy + tech) pretty appealing, and it's format was better for skimming the news a lot better then the other aggregate sites -- including HN. I also got very comfortable with Digg not being "real time", such that I never had to seek out the news. Rather than trying to read everything, and follow every story from beginning to end, I just wait for the good stuff to bubble to the surface, and then I skim over just that.
It's never a good idea to get all of your news from just one source.
Digg was a news aggregate, it includes from many different sources.
I get almost all my news from HN, but that's not necessarily bad. If I was LOOKING for news, and using it AS A NEWS SOURCE, it would be. But I'm not- the news just sort of comes along for the ride.