Why do we keep running into this problem over and over again? Why do we need one package manager per programming language? Why is software distribution so damn hard?

Because general purpose package managers suck at dealing with the concerns of individual programming languages. E.g. installation paths, virtual environments, different compilation methods, etc.

There is also no single cross-platform package manager. Mac has macports and homebrew, windows barely got one, linux has yum, apt and others. As a language designer, you don't want any part in this, you want your code to work. So you make your own.

edit: To clarify, I'm suggesting that we're stuck in a local maximum - now that all these systems already exist and have widespread adoption and tool dependency in their own environments, there isn't much of an impetus to use Nix or something similar even though in the grander scheme of things it'd be way nicer.

- The "puts things on disk" part (posix "install" or a low level tool like dpkg or rpm is most like this)

- The "determine what needs to be installed" part, (aptitude, yum)

I'm all for a per-language or system version of the latter, but once that's done, you should generate packages installed by the former.

Heck, wrap all the commands (cp/mv/install/chmod/chown/etc.) that write stuff to permanent places on disk to actually do "add to a package", give it a basic name/version number, and have the low level tool handle adding/removing it from the system (or multiple systems, or deploy it, etc.). All the dependencies, compatibility, etc. are handled by the higher level system.

This gets you the best of both worlds - system level packages, and the ability to install whatever you need. FPM (https://github.com/jordansissel/fpm) is a pretty good example of this philosophy.

But, instead, we get every punk ass CPAN descendent spraying it's crap all over the filesystem, needing the whole build environment installed, touching the internet in weird ways that don't guaranteed repeatable behavior, etc. sigh