Maybe because someone who is more than 90 days on HN isn't considered a newbie. That's plenty time to get an idea about the community. Besides, most fair play guidelines are universal and common sense and do not really require to be dug out from the dark.
p.s. Just in case you think so, I have not down voted any of your comments and am newbier than you by a shade.
p.s. Just in case you think so, I have not down voted any of your comments and am newbier than you by a shade.