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. And with a lot of tinkering, they might even be able to develop a variant of the Big-Ass Fireball that Dr. Wildebeest, pyromaniac Son of Ether, could work into his paradigm.
Some effects fit more easily into an individual paradigm when they are developed as rotes.
But Very Dead and Stinky Ancestors. Under ordinary circumstances, this is a straight Spirit effect, and he'd simply need to, say, bathe in purified water and meditate a while to focus his Spirit mojo. Mages who have a lot of free time, or very specific magical needs, will tend to create rotes of this type. Rotes can develop as a result of having to produce a specific magical effect often. The cross-paradigm and ritual uses of rotes are particularly handy.