Far more people can program in JavaScript than Lisp, and far more people use GUI desktop software that follows traditional GUI user-interface paradigms, than do things inside their terminal. (Edit: or terminal-style buffers/frames.)
So that's why my statement was limited to what "desktop software" could be. :) I mean, I use LibreOffice, which is FOSS, but I am never going to touch its code in a million years. The cost-to-benefit ratio is too high. But Atom makes doing that sound almost trivial. That's the paradigm shift.