Your first link explicitly says "As of December 2012, Windows XP market share is at 21.1% after having peaked at 76.1% in January 2007", but it doesn't really matter. Windows has lots of customers is the point I was trying to make.
Regards to the CEP, when you install Windows8 CEP is automatically enabled unless you choose to install in "advanced" mode; the CEP is opt-out, not opt-in.
Also, if a user opts out of CEP, they are explicitly telling Microsoft to ignore their data. Microsoft shouldn't take their experience of Windows into account because the user instructed them not to.
Instructing Microsoft to ignore your experience by opting out of CEP and then being annoyed that Microsoft is ignoring your experience is like young people shouting at Wall Street and then not bothering to actually vote in the election; it's inconsistent and ineffective.
Decision makers at Microsoft like cold hard data because it grounds your decisions in reality in a way that reading too many blogs and forums doesn't (although they like getting bug-reports or learning about scenarios they wouldn't have thought about).
To clarify, the first link also explicitly says "As of December 2012[update], Windows XP market share is at 39.08%". They give two numbers from two different services, the second being the 21.1% number.
I agree about the with your CEP thoughts. Whenever I actually care about a piece of software (which means I use it daily) I always join when prompted (like with Visual Studio).