Stating that there is no search box on HN is a.) incorrect and therefore b.) adding nothing to the discussion - so it seems to fit the criteria for downvoting.
Downvotes don't have to indicate "I'm punishing this user", they can simply be "this comment is low-value".
Anyway, it's too much trouble to search any time you want to post something, just to avoid setting off the blowhards around here who get annoyed.