I argue that's simply not true. Scripting languages came up with package managers because the largest platform (Windows) does not have a package manager. Actually that scripting languages implement package managers is a very good argument that their functionality is desired. As a side note, every language package manager is much worse in my experience than all of the system package managers I ever used.

I think "largest" is quite an exaggeration since historically scripting languages packaging has been rather terrible on Windows. While Windows was a consideration for languages like Python (I've read they avoided Make because of Windows), for me cygwin always coming up along with it until recently.

Maybe that's because nix and guix don't interop despite having rather similar principles, and because we mostly don't have GUI for it (like GNOME Software has integration for flatpak) nor desktop integration (like AppImageLauncher). Are you aware of work being done in this space?

All I was saying is that if a new package manager addresses all of the issues scripting languages had, scripting languages would still use their own package managers. Because the culture is now set, even new scripting languages would write their own package managers.