The CalDAV server authored by Apple and included with OS X Server is written in Python. PyObjC receives a lot of attention from Apple employees. I don't think there's much preference exhibited by Apple one way or the other.
And vice versa, there must be some Linux distros that have tools written in Ruby, right? Particularly some of the newer ones, I seem to recall hearing that their system tools were Ruby.
Read up on setuptools and the Python Package Index, aka the Cheeseshop. Setuptools hasn't yet been adopted as the one true packaging format by all library creators, but it gaining acceptance.
And vice versa, there must be some Linux distros that have tools written in Ruby, right? Particularly some of the newer ones, I seem to recall hearing that their system tools were Ruby.