Numbered lists imply completeness, omniscience etc. - it's a literary gimmick, both in terms of attracting the lazy reader and in giving the writer a convenient structure they can fill out easily, with the last few points usually being fluff. A famous example is the '7 habits of highly effective people' followed by 'the 8th habit' (strangely, not titled 'oh wait, I forgot one').

Of course, you could argue that leaving the numbers in informs HN readers about which articles are mere gimmickry rather than carefully written essays.