One possible explanation: karma. the more you "contribute" the higher the possibility that you get upvoted. Of course, if this is true it sounds like cheating

One possible explanation: karma. the more you "contribute" the higher the possibility that you get upvoted. Of course, if this is true it sounds like cheating, but no one is forced to upvote, so at the end of the day, it's more about the success of HN as a news engine.