I used to believe this about myself as well, but later realized it was a rationalization. The reality is it's because leaving hacker news for extended periods (more than a minute or two) results in dopamine withdrawal. I feel a powerful urge to return to browsing links and my brain makes up a reason along the lines of "you're wasting time by staying on this site instead of going back to hacker news." It's a similar thing that drives me to "skip ahead to the good part" in youtube videos rather than watching the whole thing, evidenced by my doing it even on videos that are very short.