Ok, now, what languages beside Python and Go provide Command line argument parsing? And Go doesn't do that in a `professional` way. You either write your own, which can easily turn into a clusterfuck or use a third party library. Even in Go, people use cobra[1]. Also embedding a lot of functionality in a standard library isn't great as well, because if some vulnerability is found, it's really hard to patch it, because you need to push versions and (for example on Linux) some distro maintainers won't push it for `stability` etc. A standard library should provide basic functionality (in most general areas), but not very advanced one.

[1] https://github.com/spf13/cobra