Because pulling in, updating and verifying code is fundamentally a responsibility of the OS. Also language specific package managers are kind of stupid.
I never thought about it, but yeah, the concept of “fetch a repository of packages, resolve dependencies, download a tarball and put it in a special place on disk” is such a common operation that it should have been solved once and reusable across languages or anything else that needs this process (editor plugin, font management, gamedev and audio assets, OS packages, app store, etc.)
Yet any language has to reinvent the wheel and write yet another archive downloader.
> Yet any language has to reinvent the wheel and write yet another archive downloader.
No, I don't think they need to do that. They want to do that instead of using the already existing OS packager, breaking and messing up things left and right.
Take for example the ridiculous state in the python ecosystem. It would be entirely eliminated by using the existing tools of make altinstall, the system-package manager and properly using Site files. I don't know when altinstall was introduced, but in this issue from 2013 it is already mentioned: https://bugs.python.org/issue19553 .
The OS package managers already go out of their way (e.g. Debian) and renamed site-packages to dist-packages, so that OS installed and other vendored python packages don't conflict. The Python maintainers provide make altinstall and the python program provides site files. Linux distros have /usr/ vs. /usr/local to avoid programs conflicting with the OS versions. So many problems could never occur by people using their tools correctly instead of adding layers on top, which causes other breakage and is "fixed" by even more layers on top.
