We're so used to notifications that we probably never stopped to think about how to implement them. It might be trivial at first glance. However, in a distributed system, we might face more challenges requiring techniques we don't expect when implementing a notifications infrastructure.
When it comes to distributed systems, autonomy is a guiding star, and coupling is the villain trying to sneak in at every step. Orchestration is a particularly subtle form of coupling, usually detected when it's too late. However, the root cause is somewhere else.