Possibly because the poster does not include a first comment.
This is usually done by self-important bloggers who feel no comment is needed, so all-encompassing are their “articles”.
Don't think that is why. I often don't comment when I put up a post and there is others are still able to answer.
Ever wonder why the fund raisers take so long? Could it be the “self-important”, self appointed blog police such as yourself make people think twice about donating?
That only happens when someone has comment #1 yanked by the Mods. That usually happens because someone tried to skirt the “must excerpt” rules by posting material beyond the required excerpt in post #1.