Starting with Internet Explorer 8, Microsoft provided built-in developer tools for Internet Explorer. IE8 provides IE8 Standards, IE8 Compatibility View, IE7, and Quirks Mode. IE9 provides IE9 Standards, IE9 Compatibility View, IE8, IE7, and Quirks Mode.
I have often wondered why Microsoft choose to provide IE6 testing VMs instead of offering it as a convenient browser mode, while still providing Quirks Mode. Nobody wants to fire up a VM (now or three years ago) just to test a random IE6 report, so why did Microsoft choose to make IE6 testing so difficult for IE7 and every version following? Has Microsoft ever commented on that decision?
EDIT: I know IE6 should be avoided and Microsoft wants to wipe it out for good as a browser. My question is looking for historical significance. I am wondering if Microsoft ever publicly announced that IE6 would never be supported by developer tools from IE8 on, which was released at a time that IE6's market share was still significant to developers. Even X-UA-Compatible Document Compatibility Modes lists everything, including IE5, but IE6 is missing from the list. Perhaps Microsoft began phasing out IE6 through developers long before they made a campaign targeting users, but I'm not sure why they provided VMs at all if that is the case.