(if they did Microsoft would have gone out of business years ago), the embedded market is a different ball game.
Refer to
www.windowsfordevices.com for examples of embedded Windows devices i.e. Microsoft applies market segmentation for its products. It would be unrealistic for Microsoft and is its value adding partners to offer a full Windows XP install on a limit role computer.
PS; They made "small" profit on embedded related activities (minus XBOX).
Desktop users don't put their machines through that sort of abuse so machines don't need to be so reliable
What kind of abuse?