One use-case would be for including dependencies in a repo. For example, it is common for companies to operate their own artifact caches/mirrors to protect their access to artifacts from npm, pypi, dockerhub, maven central, pkg.go.dev, etc. With the ability to efficiently work with a big repo, it would be possible to store the artifacts in git, saving the trouble of having to operate artifact mirrors. Additionally, it guarantees that the artifacts for a given, known-buildable revision are available offline.