It's upvoted because, after people post a comment utterly destroying it, they want their comment's unique wisdom and intelligence to be visible to others. Even (maybe, especially) when the original article is garbage.

It's a perverse incentive problem in social news.

Well, i will add that the major determinant for whether an article stays on the front page is whether there is an active discussion.

So the more chatter there is, the longer it stays on the homepage. The longer it stays on the home page, the more people upboat it without reading the post or the comments.

But that's me retreating to the study of aggregate behavior. sigh

Because it's interesting. I usually read the comments and not the article.

I've almost gotten to the point where I don't read the comments. Quality has (subjectively) been declining over the last couple of years.