Why are some important Windows Updates not checked automatically?

Question

I often find that there are updates for Windows. Most - but not all - of them are automatically checked, even though they are all declared as important.

Why are some of the important updates not checked automatically?

Answer 1

If the update is unselected by default, it is tagged as an optional update. There may be issues with the patch itself so they don't push it out directly. The patch may also not be ideal for all environments, such as a language pack or .NET update (which have broken things for me in the past).

Answer 2

Note: Some updates shown in the update list aren’t downloaded with the other updates, and you aren’t notified to install them (described in KB910340). Some customers call support believing that WU isn’t working correctly, because it isn’t downloading or notifying them about some updates. These updates are held back by WU. You can download and install them manually through WU, but WU won’t automatically download or notify you about these specific updates until the WU servers make them “available” for your computer. We gradually allow computers to start downloading larger updates, like Service Packs, because they are bigger downloads that require more network bandwidth to download. If an update is held back from your computer, it will not prevent WU from notifying you on the system tray after all of the “available” updates have been downloaded.

Excerpt from Microsoft Update Product Team Blog

Answer 3

In addition to what John T says, there may be requirements that certain patches (usually Service Packs) be installed separately from other patches. Service Packs are not just for the OS but sometimes for application frameworks (.NET and the like) as well as other large or important suites of software (Office).

Running Windows Update will usually select the Service Pack automatically and deselect all other patches until after the Service Pack has been deployed successfully, or vice versa, depending on the circumstances.