I´ve got this old -and bad- habit of building everything possible in each and every province, I don´t like unused build options left open. Of cource, it´s a waste of resources and I know it is, but, as the saying goes, old habits die hard, especially the bad ones. A try to specialize only a few provinces had almost proven fatal one time when the French took Aquitania, my sole cavalry-producing province, so my first try in a streamlined production setup almost proved fatal.