It may also be because in the early stages, there's not enough production of liquor and wine to allow the production of some units in the vast quantities that would require. The devs might have thought it better to make armies with weaker types of divisions rather than not being able to build enough divisions. Besides, armies composed of 50% Artillery were NEVER fielded historically, so it doesn't make sense to make that "normal" in the game. In my opinion, there should be restrictions on how high a percentage of artillery you can field, without suffering efficiency penalties, and doctrines/techs that gradually allow you to use more over the course of the game.