Long answer: Sometimes you can do that, yes. But you'll run into issues with "modern" frontned toolchains and complicated packages where you want to write ES2017 code, transpile it with babel, bundle it with webpack, make a universal lib, etc., and push the result to your package repo, but not commit it to your git repo.

Gitpkg handles all the wierd corner cases, and lets you keep build artifacts out of your git repo, and raw source out of your package repos. And if you use github you can even use the github IDs in your package.json, but the result is going to be a lot better. If you're just writing a plain one file package for use in node that doesn't need any processing, eh, no need for gitpkg.