Seems that any Mage worth sending a Publisher's Clearing House Sweepstakes entry to would have better things to do than resort to predetermined spells. But recently, while Jason Corley and I were talking about the importance of a coherent paradigm for Mage characters, I realized that there were, in fact, some compelling reasons why rotes would be created and maybe even used.
Rotes are good educational tools.
Most mages receive some kind of instruction in their art, but most mages also have their own peculiar rationale for why magic works. Rotes can smooth over differences in individual paradigms, both within a Tradition, and between several Traditions. For example, let's think about two Order of Hermes mages who have a preference for showy, stereotypical vulgar effects, particularly the ever-popular fireball. In Black standing at the end of the street, and is rewarded with a nice big ball of flame. Joe, on the other hand, weaves a Sigil of the Hallowed Salamander between the all-powerful Sun and the wretched target, focusing the Flames of Helios Itself in a spherical area, with the usual destructive effect.