You know the authors never submit the blog posts to HN, right? It's other HN members who are a fan of 37 Signals who submit their blog posts to HN.

So, are you complaining at 37 Signals for writing on their own blog, or at HN members for submitting something they thought was interesting?

Also take note that the term "HN-worthy" is highly subjective. Submissions make it to the front page of HN not because they're HN-worthy but because many people vote them up.