If you write JavaScript or TypeScript, you already know the feeling: a dozen old project folders, each carrying a node_modules directory that's 200 MB to several gigabytes, and collectively eating 20–60 GB you'll never get back by tidying Downloads. node_modules is the single most reliable disk hog on a developer's machine, and the worst part is that it's invisible — buried several folders deep, never showing up where you'd think to look.
Every project installs its full dependency tree locally. Transitive dependencies multiply, native build artifacts get cached, and nothing cleans up after itself. A repo you haven't touched in eight months still has its entire node_modules sitting there. Multiply that across every side project, every cloned repo, every tutorial you followed once, and the number gets large fast.