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. After all, you aren't really learning anything new about Reality or your powers, and well-practiced rotes become almost akin to static effects. On the other hand, if your Avatar has a Pattern or particular type of Primordial Essence, rotes are pretty satisfying things. I figure the Traditions would have varying opinions on rotes. Consequently, they produce a lot of rotes, practice a lot of rotes, use a lot of rotes, and teach a lot of rotes.