Regarding the friends and profile visitors, it's just a new feature that came with the software upgrade. There is no "why" specifically (i.e. those features weren't added with any specific intent), and the info isn't "used" for anything. It doesn't have any detrimental ramifications unless you're a stalker.
As for why this page doesn't show up in the new-post section, are you talking about the block at the top of the main page that shows most recent posts? That block, I believe, is not 100% dynamic, it seems to be updated on some interval that, depending on how fast new posts are being made, might "miss" a thread if enough posts were made to other threads between block updates.
