I also use GNU Guix and Shepherd on top of Ubuntu at work. Shepherd manages all of my user daemons (mostly Ruby web application servers) and Guix as an RVM (and other such tool) replacement. Is that practical enough?

There's a big difference between "practical" and being the foundation of software (and I guess people ARE still trying to make that happen; it's not a strawman).

Emacs Lisp is probably a better example of practical.

Or LispWorks or Franz Allegro (esp AllegroCache) that have made real money for years by letting people code circles around others with better tooling. Scripting languages have closed the gap a lot but not fully. I'd say at least two commercial tools are quite practical.

Sure I agree that both are examples of real software written in scheme.