I am one of those who believe that it is always good to have the latest versions of any program, but I know that some folks think differently, and prefer to work on the "if it ain't broke, then don't try to fix it" principle!
I realize it is not easy to grasp the Debian release cycle, but it releases new stable versions roughly every two years.
Debian consists of several branches - experimental (for developers), sid (still in development), testing (means testing) and stable (really stable).
Raspbian is a custom Debian testing. About every six months or so before the initial release, testing is frozen, until it becomes the new stable. Testing/Wheezy froze this summer. (After that, testing starts rolling again.) It means no new versions of anything from the Debian repositories, just bugfixes and security fixes. (I understand it is a little more complex than that for Raspbian, since some applications are custom for the raspberry pi and grabbed from git, like omxplayer.)
What I am trying to say is: No upgrades = no bugfixes and no security fixes.