Why is there no Windows Update for XP Embedded and Windows Embedded Standard 2009?

Microsoft published a blog article explaining why XP Embedded and Windows Embedded Standard 2009 cannot have Windows Update.

You can read the whole article on the new Approaching Embedded Intelligently blog: http://blogs.msdn.com/b/windows-embedded/archive/2007/04/04/why-can-t-i-use-windows-update-with-xpe.aspx