Sage does nothing, so just saying "sage" is pointless. The idea is that you use your non-post to register why the thread is a bad thing. Just saying 'sage' is the same as walking into a room and saying 'I don't like Naruto' then walking out again. You aren't getting anything done.
Applies just as much to people complaining about sagers. Doesn't do anything. Everyone already knows you aren't meant to like Naruto, so saying it is kinda dumb.