Take, for example, Burning Blood which is a rank 2 Bright Wizard spell. It has no "additional modifiers" cost, not even a . There are other rank 1 and rank 2 spells of the various colleges with no costs whatsoever, or with just a single . I really don't think being able to cast "automatically", especially with rank 2 spells, is the intent. I really do feel that the intent is for spells, and most tasks, to be "easy" and not "simple". It's purely up to the GM, though, since it is generally an Unopposed check.
Refer to pg42 for the descriptions of the challenge levels.
Simple is basically -> "something so basic and routine that the outcome is rarely in doubt." i.e. success is assumed to be automatic except in extenuating circumstances.
Easy is basically -> "something that should pose little challenge to most characters, but something could go wrong". ie reasonably expect they will always succeed.
Average is basically->"a routine action where success is common enough to be expected, but failure is not surprising". ie. will succeed more than they fail.
IMO, spellcasting is something that will pose little challenge to a trained wizard, but failures do happen. The Winds of Magic are not docile and benign. It takes a modicum of control and attention to control the power and shape it into the function of the spell being cast. It isn't something most wizards can do on auto-pilot unless they are very experienced. Certainly not apprentice wizards.