For me, reading HN is like reading the paper or reading books about subjects that matter to me: it's not time strictly spent on the job I have to do, but it's part of a healthy information diet. Crunching code without taking a look at what's currently happening and being discussed in your professional community is hardly a recipe for self improvement.
(It's a thin red line between healthy consumption and abuse, I know, but our job often _requires_ that we keep an eye on what's going on outside our compiler.)