The guide is written for In Nomine (and earlier), in which there was no way to generate good advisors with cultural tradition. With half-decent Masters of Mint being far from a sure thing to get randomly, NB was next to obligatory to get any amount of cash without causing inflation. It's priority went way down with HTTT due to the ability to get 5-6 star MoMs almost throughout the game, rather than 1-3 star ones occasionally.