Just because every forum, whether its SMF, Vbulletin, IPB, phpbb etc etc has a new or latest posts link. That's just what forums have.
So people can view all the latest posts/replies etc without having to choose a sub-forum and see whats new they can see whats new from that.
Not sure why you need a screen shot to understand it any better.
Its just a nice feature to have. :)