For the record, Tcl doesn't use garbage collection, rather objects are reference-counted and freed when ref count is <= 0.

But interestingly, Tcl is a good example of languages that took a piece of Lisp's domain. In fact, Tcl is quite Lisp-like with a syntax distinct from Lisp. Tcl has been successful and with the recent release of v. 9.0, it stands to gain traction among programmers.

OTOH CL and Scheme remain underused though current implementations are generally well-equipped to handle contemporary requirements. I've used Scheme to build website generators and other tools but there's a dearth of large-scale, visible Lisp/Scheme projects out there to attract developers.

Starting such a project is a big commitment, probably programmers are hoping somebody else will pick up the ball and run with it.