I was recently very surprised to see an expensive security scanner which builds apps as the service account apparently without sandboxing. A package manager which executes code or which is exploitable would give you access to what is very likely an interesting account & data, and in at least some cases might not leave many clues behind. PyPI, etc. at least has centralization and immutable versions but who knows what's serving some random repo, tarball, etc. which might not even be a direct dependency?