Eternal September, I don't see any other explanation. Maybe a link to http://ycombinator.com/newsguidelines.html should be displayed more prominently.

Also, there are a lot of off-topic submissions that serve no purpose at all. Flagging them helps, but not always. I understand majority of folks here are web oriented crowd. Fine. But do we need a submission every time Apple lets a fart out, or antenna issue PR war - what does that have to do with 'Hacker News'.