I think we're getting into matters of definition. Do I count on HN to stay aware of current events? No; it would be a very incomplete picture. Much of HN has nothing to do with current events.
> This only has to do with mismatch of the scope of HN and the scope that you are interested in.
It's not scope mismatch, it's that HN doesn't present a (nearly, roughly) complete picture of current events in any scope (other than the scope of itself, of course).
Probably not mainly, but isn't this one of its functions?