Guile scheme was meant to be use as a "scripting" language, to extend and customize software. As far as I know, from the GNU project, only GnuCash and Lilypond use it.
Very few of the software from the GNU project have been written by RMS, they are often starten outside the GNU project and join or get adopted later.
It's very easy to do hyperbolic statements like lauding lisp, it's hard to use it in practical situations.