Because it's still missing features that might seem essential if you decided what was essential a priori instead of empirically.
When you started Hacker News you wanted a site which you could moderate and where users could only upvote (even though users of a certain karma level can downvote), according to Huffman's interview on mixergy. What features did you think were essential a priori that you left out?
this was an hilarious joke by PG, lost on the humourless HN community.
Don't you mean lost on the three people that upvoted pmarin's comment?