Best i can tell, the reason Xfce seems to assume it is there is because the developers are short on time and thus make use of low level Gnome libs to get things out the door.<p>Essentially Gnome seem able to throw a whole lot more man hours at various topic than can the rest of the DEs, KDE included. This in turn seem to lever Freedesktop towards them (though Freedesktop may have overly favored Gnome from the get-go).