You are maybe being downvoted as you stated it so bluntly, but I'm not sure your point is without merit.

The HN audience do not necessarily represent the mean/mode user, and Facebook are in a numbers game really.

I agree with most of the sentiment above - I wish I could filter posts that are just attachments, 3rd party junk, and tune the algorithm to show me posts from a core set of friends, but I also recognise I don't use FB like a most people, I imagine.