Nature (and evolution) can be both abundant and parsimonious. Abundant might refer to the explosion of life-forms around the time of the pre-Cambrian. Or, in our day, the extraordinary way that insects and flowering plants interact (and drive the speciation of each). Maybe one can think of these as evolutionary windows of opportunity.
In this case (emotion), my guess is that parsimonious applies. When there’s all that useful circuitry in the cerebellum (emotion), why reinvent it in the cortex? The cortex obviously has new and very useful circuitry but there will still be many applications where the old circuitry - and thus the cerebellum and emotion - are what’s needed.
Emotion has been around a much longer time than reason (and is found in a wider range of animals). It’s true that it was probably easier for evolution to invent emotion but history is also telling you that the evolutionary advantages of emotion are longer-standing and better tested than reason. Current events tell me that the evolutionary jury is still out as regards human-type reason - or at least the way these various quantities (reason, emotion, intuition, etc) are wired together in the case of human beings. Evolution may need a redo.