I had very limited contact with CPAN some years ago but I imagine it was slightly more sane in terms of granularity of dependencies.

Whereas a lot of npm modules are relatively small - some tiny - and have their own dependencies. So a simple "npm install blah" command can result in dozens of packages being installed. Dealing with that manually would, in fairness, be a giant chore.

Now of course there's a discussion to be had about whether thousands of weeny little modules is a good idea or not but, to be honest, that's a religious debate I'd rather steer clear of.