These features are useful whether the code you're writing is pure, stateful, object-oriented, functional, and/or whatever paradigm you write up tomorrow. Forget aesthetic arguments about elegance; where else can you build so much without ad-hoc concessions to individual language features? As far as I know, there's no other method that lets you treat powerful language features as libraries without either (a) making a mish-mash when they're used together like compiler plugins do (b) making debugging your compile process a full time job like various strongly-typed macro systems tend to.
Why not use FP to form the fundamentals of our languages, something where as of yet it has no equal, and build up the structures we need (regardless of programming tradition of origin) on top of that?