One of the main benefits of the long-form article is that it presents conclusions in a tidy order. Dead-ends and objections get edited out so that the reader gets the result without the roundabout route that the author takes to get there.
A reader can still question any step the article states. What they cannot see is everything that was left out: whether the author already considered the objection they are forming, what evidence a claim rests on, or which term was quietly assumed. If the article doesn't address their objection, they can't tell whether it was answered and cut, or never thought of.
Writing the article also costs the author something. The connections between ideas, the order in which they were worked out and the reasons for discarding alternatives mostly stay in the author's head, and are lost once the piece is polished.