Because 99% of long articles are a waste of time that could be summarized in a sentence or two. This is why no one reads articles here or on Reddit, and just skims the comments instead.
I almost always at least skim an article before diving into the comments. Many times I will read the whole thing, especially if it is short, as this one is. I do believe that most probably don't do that. It's often possible to tell which commenters have read it and which haven't, i.e. if a comment mentions something not even present in the article, or if it mentions something clearly refuted in the article.
I think it's important to read the things you comment on, and I think it's important to expect others to do so as well. Ignorance is tolerated too much these days, especially considering that knowledge is easier to obtain now than ever before.
A lot of long form articles are like online recipes though: A giant barely-related narrative about the subject’s home town and hobbies and life philosophies, and hidden within are the 5 lines showing ingredients and how to cook the food.
Perhaps this is why a lot of comment threads quickly become arguments about the first thing that springs to commenters' minds when they read the headline rather than what the article actually says.
