A MacTrast’s source, directly in contact with Apple, reports that this is not a bug issue. He says that it wasn’t a coincidence that support site of Apple was free from iWork, Aperture and iLife download updates. They are also not present in the Software Update system. And Mavericks changed how updates were being distributed for legacy app versions.
Rather than maintain separate updates for these in addition to the Mac App Store versions of each app, Apple has decided to eliminate their legacy software update system for apps entirely. Instead, when Mavericks discovers legacy apps installed on your Mac, it provisions them as a Mac App Store purchase using your Apple ID. It saves us a lot of time, effort, and bandwidth. After the provision is complete, it will appear in your Mac App Store history as though you have purchased the Mac App Store version of the app. While we are aware that this enables piracy of our apps for unethical users, Apple has never taken a strong stance or action against piracy in the past. We like to believe that our users are honest, even if that belief is in vain.
As a side note, Apple also made iWork and iLife apps available for free, but only for those who buy a new OS X device or an iOS device.
