Follow the first link in the github description of Bordeaux-threads and you reac...

_19qg · on Dec 3, 2016

The page is here. Send the author a bug report...

https://common-lisp.net/project/bordeaux-threads/

> Also, if it is so portable and so useful, why hasn't it made part of the language and of the various implementations?

You make it a part of the language by loading it in.

    CL-USER 23 > (ql:quickload "bordeaux-threads")
    To load "bordeaux-threads":
      Load 1 ASDF system:
        bordeaux-threads
    ; Loading "bordeaux-threads"
    [package bordeaux-threads]...
    ("bordeaux-threads")

> Why there are no updates to the standard?

Because it is too expensive (it's an ANSI Standard, which makes things difficult), there are no sponsors for it and not enough are interested to do the work.

The language evolves in libraries, portable substrates and implementations since some time.

Note that the language has a lot of flexibility for change built in: reader macros for the s-expression syntax, macros for the Lisp syntax, meta-object protocol for the object-system, packages enable new Lisp dialects, ...