It's not really arbitrary. Python is an outstanding glue language, maybe Ruby or Haskell could compete (how is Perl6 nowadays?), but none of those you mentioned.
Rakudo Perl 6 is doing very well indeed, thank you. First official release in December 2015, second official release in November 2018. Monthly developer releases. See https://perl6.org for more information.
I agree that Python is great as a glue language. Maybe "arbitrary" wasn't the right word to use. What I meant was that Python hides what actually happens in exactly the same way that lower level languages do, just at a higher abstraction level.