Because it's been years in the works, it's finally about ready, and Racket only now is in everyone's mouths? Guile is now also able to run other languages as well, like Javascript, or at least so their maintainers claim.

Besides, I know that among users of fringe languages like us (you too are, I presume) this is a bit of a taboo question... but who uses Racket so much as for it to make a difference here?

Emacs is an RMS-run GNU project.

Back in 2002, the better choice was Common Lisp. One of CLISP's authors even made it work with Emacs over the course of a week-end [1].

There's never going to be the perfect fit for an embedded extension language. Hey, wasn't that what Lua wanted to be, and Tcl before it? Guile certainly isn't the easiest fit, but it's the only one that will get accepted.

At least, if they slowly change the actual extension language away from ELisp, all extensions that rely on external programs will survive better.

[1]: http://lists.gnu.org/archive/html/emacs-devel/2002-08/msg000...

Because Emacs is the ultimate GNUtoy.

Guile is a very capable Scheme implementation that was made to be the official GNU extension language. It features a very nice C API and FFI. Racket and Guile have different design goals. Guile fits Emacs' edit-the-editor-while-you-edit paradigm better.