Yes, that's for the OS. But every application has its own update mechanism. And since there's not standard package or update system on the Mac, they're all different and can't be controlled centrally. There isn't even a standard way of removing applications or finding out what's installed.
Apple's apps - Safari, iWork apps, QuickTime, iTunes, etc. - all use the same utility application. to update themsevelves. If every one of those programs I listed changed since the last time you ran it, they all get listed at once. You do not have to run it one time for each.
As for third party applications, they really do not update all that frequently. Most seem to check for updates when they launch. If you are behind, they tell you and offer you a chance to update right then.
A lot of Mac apps seem to use Sparkle to handle their updating: http://sparkle.andymatuschak.org/
It would be nice if the Mac came with a package manager for third-party applications. Like Red Hat's RPM, or Debian's, or whatever.
I know it has been talked about but I do not know if one is forthcoming.
Mac apps do not seem to need complicated uninstallers like Windows apps.
Not sure, but it might be useful for printer/scanner drivers/apps. They seem to install a lot of stuff. Anything that installs a kernel extension would be nice if there was a standard uninstaller. Usually, the drive image for the product includes an uninstaller but that is not particularly useful place to have it.