But then it actually does get back to the language because the reason people build NumPy and SciPy (and Django and tons of stuff in other domains) is that Python is, after all (despite its warts) so damn easy to use. Making it easier to build all that stuff, and more rewarding also (because there's an audience).

Which is not an extra but in fact means a heck of a lot for a language's chance at long-term acceptance.