I have a theory, of sorts: Western culture values quantity over quality. More is better than less. Big is better than small. Perhaps it has something to do with the dualism created by Judeo-Christiana theology?
Whatever the case, it may account for the increasing length of blog posts to do with the business of publishing and writing of books. Ironic really, that people offering ‘advice’ cannot do so succinctly in an industry where getting to the point is the point.