Ask HN: why do you upmod?

In my daily reading, the front page of hacker news has become precious intellectual real estate. However, the window for a new article submission to reach critical velocity and land on the front page is very small, due to the large number of submissions. It has made me curious - why does each person upmod a particular posting? In the community guidelines, relevancy is defined as "anything that gratifies one's intellectual curiosity". Yet I am continually surprised at some of the articles that get the MOST upmods. Sometimes finances and politics. And, while the NY Times and TechCrunch are often interesting, are they truly the pinnacle for gratifying one's intellectual curiosity as the cumulative upmod votes might indicate? Once I have understood the community here, I find myself trying to be disciplined.. silently asking myself 'did this topic make me curious?', 'was the content intellectually gratifying (after I read it)?' and finally 'do I want to see more articles like this on the precious front page of HN?' So, I'm curious, what is that silent question that goes through your head before you click that little up arrow?