Fundamentally, I think it boils down to the fact that node's module loader is dumb, and npm doesn't try to be a smart module loader on top of that - it just ins

Fundamentally, I think it boils down to the fact that node's module loader is dumb, and npm doesn't try to be a smart module loader on top of that - it just installs dependencies to where node's dumb loader will be able to find them. And, because of CommonJS, it's easy to tell it exactly where it's allowed to look. One way this manifests itself in a nice way is with local installs - let's say you have a package that depends on modules A, B, and C. Each of those modules has its own dependencies. The default behavior when you install the package is that A, B, and C have copies of all their dependencies (so if all 3 depend on D, you get 3 copies of D), and so forth all the way down. This does waste disk space, but for the most part node modules are small and disk space is cheap. The advantage is that you don't have to worry about conflicting dependencies, or subtle changes breaking things in hard-to-find ways. Like a sibling commenter said, I have no idea if this model will transfer well to Rust.