If some developers want to use some new language, they have to first in put in the effort by a) demonstrating the business case of using a new language and allocating resources to integrate it into the ecosystem b) porting all the shared codebase to that new language.
Of course, this is the exception to the rule you described well :)
Throughout my career nearly every single company I've worked in had That One Codebase written by That One Brilliant Programmer in That One Weird Language that no-one maintains because the original author since left, the language turns out to be dead and because it's extremely expensive to hire or train more people to grok that language just for this project.
This is basically the same set of languages people were writing 20 years ago and will probably be the same set of languages people will write in 20 years from now.
For some (like me), it's more a superset of C, assembly, bash, maybe lisp, python and matlab.
For others, it's going to be JavaScript, PHP, CSS, HTML..
I agree though that a library is usually domain-specific, and that you can probably easily identify the subset of languages that you really need official bindings for (thereby making my comment a bit useless, sorry for the noise).