IMC, spellcasters get a number of bonus 0-level spells equal to their spellcasting ability bonus. This gives them a slight (needed) bonus at 1st and 2nd level, and becomes a non-issue afterwards. Also, it adds to the flavor of a high-level mage who never has to lift a finger and always uses cantrips for even the most trivial tasks (e.g. flipping through the pages of his spellbook).