The slow rate of ie adoption is from corporate users who are reluctant to update more frequently because of the risk of breaking their internal applications. If this was any other browser I am guessing the chart would have looked the same.
Microsoft apparently can't do that because of all those corporate customers which depend on subtle behaviors of a particular IE version they have apps developed against. This is a vicious cycle. Auto-update would work if it was the case from the very beginning.
I think they provide "blocker toolkits" with registry keys so Windows Update offers security updates for the current version of IE instead (all versions of IE follows the support lifecycle of the Windows version it is installed on).
Don't forget server versions of Windows. Server 2003's IE6 is going to be supported until 2015 and Server 2008's IE7 is going to be supported until 2020. And worst of all, Server 2012's IE10 is going to be supported until 2023 and can't be upgraded to IE11 without upgrading to R2.
Do people generally surf from Windows Server though? Or run webapps using Windows Server? I could see someone using Windows Server to go to a website and download a file needed for the server, but that should only affect roughly no one. If your website supports SMB or enterprise customers and your downloads aren't accessible on even IE6, you're massively misjudging your audience (and putting too much into your web development).
It would be interesting if someone published the 'effective browser technology guide' which defined the set of things that would look the same on all browsers. It might end up with just CSS2 and tables though :-(
Or as an album of just the charts: http://imgur.com/a/3UM4J