This depends on languages. For c/c++ without a package manager, people hesitate to add external dependencies (and especially when high performance is needed, e.g. game engines).

It surely does, but I think in most languages it is a bad idea, to add a external dependency, where it isn't needed. Like in the cases I mentioned, it was just standard stuff, already covered by the browser standard libaries.

So when I just need a simple connection to a web socket - I don't need that external baggage. But for high performance graphics, yeah, I won't write all the WebGL code by hand, but use Pixi (with the option of writing my own shader where needed).