Most don't, but Facebook does have its own equivalent of jQuery, lodash and angular. A few other very large tech companies are similar.

Most C++ shops don't have their own equivalent of Folly, they use Boost or Google's Abseil or something else.

I think that's the key point, the scale in which this starts happening is the sizes of the Googles and Facebooks of the world (in C++: Abseil and Folly) but also in Java (at Google: Guava), JavaScript (at Google: closure, Angular/Polymer/Lit/and many others).

So people extrapolating from a ~100 person company or a ~1000 person company using JS might as well think it's about the language, but it's really about the size, I think.

Closure isn't so much a standard library as a typescript alternative though, I don't think the comparison works.

Look at Google and the Closure standard library for an example of a company writing a lot of JS that ended up writing it's own "standard library"-like thing.