That's just a recognition of the existence of that particular quirk of Arch, and that people may need to cope with that. It's remarkably painful, in practice, to deal with the one special distribution that makes "#!/usr/bin/python" do the wrong thing. And unfortunately, some other distributions don't have a "python2" or "python3" binary, making it painful to write portable scripts; you can't write "#!/usr/bin/python2" or "#!/usr/bin/python3" and expect it to work on every distribution out there.

As mentioned, Debian is working on migrating scripts to support Python 3, and doing so using /usr/bin/python3 , which already appears in the shebang of a large number of Debian's Python programs.