What does an "importer" do? I.e. is there some reason to use Guix when you can just use the package manager all other Racket and CHICKEN users use. Or Akku or Snow for R6RS and R7RS.
And about Guix and Scheme. Maybe Guix users are not Scheme users primarily, but they are there for what Guix gives them, and Scheme is just how it is made. One day they will do a coup and rewrite it in Java.