Isn't that what newbies are for?
Seriously though, this is a web-wide thing to do on forums. It doesn't matter what sort of forum I'm on, there's always
some newbie who will dig out & bump some of the most old, stale posts on the forum.
I guess I'd like to think it's nice that they are reading the forum topics that deep into the site, because I can't think of any other answer as to why they find such old posts to reply to.
Anyway, sometimes some interesting ones do get bumped & the thread will take off for another half dozen pages or so. Not so bad, in that regard.