Why should people use emacs to run applications when the shell already does that just fine? Just use the shell and you can run applications in any language you want rather than having to stick with elisp. If you want to constantly switch between applications, you can use tmux or simply your terminal emulator's tabbing functionality. You can even switch between GUI applications instaneously if you use a tiling window manager like XMonad.
Emacs is my shell. You don't have to stick to elisp either, you just need a little elisp glue. (The Emacs interface for the GNU Guix package manager, for example, is written in Guile Scheme for the most part.)
Emacs is trivially extensible and whatever I make it do can be used in other sub-applications. I can evaluate code wherever I want and change the system at runtime. It's quite a different feel compared to having "unglued", ununified applications.
