No need to have a configured builder to evaluate the derivation graph
Evaluator simplicity
It will also enable me or someone else to create a LSP that interprets the expression with intermediate steps and gives you suggestions, without taking a year or doing anything impure or requiring a builder
Indeed, this is also the reason I am (eventually) planning to add a language agnostic plugin boundary to eka. I imagine most things you might want IFD for you can do more easily in the native language of concern, and then just feed them into the evaluation via a json stream or something