My system package manager has root access, it can make or break my machine. As a user, I am trusting the distribution I use and it's package maintainers. Package vetting, stability testing and signing are what I expect from my distribution.
For language specific package managers, those things would be nice, but completely unreasonable to expect. There is no trust involved, how can there be? Most package repositories have no vetting process, it's publicly writeable.
For python, there is virtualenv. Packages are "installed" in their little environments with user privileges. For node, I personally have a dir in home for modules and then ln -s cli tools into ~/bin. Again, all with user privileges.
The crazy thing is, for some people there is no distinction. In fact, I noticed a trend in the node community in that they all give instructions to install their modules globally. Literally every single installation instructions I have seen for node cli tools have said the same thing, install globally.
This is pretty baffling. If you were on a Windows machine, would you download some random setup file from a public ftp and run it as administrator? I don't know why an entire community (of power users and developers no less) seem to think it's somehow acceptable practise.