Uh, when was the last time you saw XP on a new machine - from Google Analytics on a UK retail site I'm getting 2.4% of users on XP this month, equivalent month in 2013 was 6.5%, in 2012 was 12.4%, in 2011 21%, 2010 34% - that's basically halving each year for the last 3 years.
Yeah, this is because your users are mostly in the U.S. or Western Europe. It's a different story elsewhere in the world (although even those countries are slowly moving off of XP).
