The reason is that the general concept of smaller government, lower taxes and reduced spending makes for great politics.  However, actual spending cuts make for horrible politics.  That's why we rarely see a list of proposed dollar for dollar cuts from majority caucuses.  Instead, cuts are proposed such as the Office of the First Gentleman that make for good partisan politics but don't provide for substantial savings.  Another way to avoid suggesting substantial spending cuts is Nick's love of the word fungibility.  Which simply is a way to say "take it from somewhere else" without having to say where that somewhere else is.