Just my personal story, but perhaps extrapolating from it will help answer your question.
At my job I use Python because, well, at some point before I arrived one of the senior developers went on a jihad against Perl. :-)
I've read stuff about Ruby and while some things about the language intrigue me, it seems that any application you can build with Ruby can also be built with Python. If I'm going to learn another programming language in my Copious Free Time, I want to learn something really different from what I already know, not something that has pretty much the same features with different syntax and libraries. So Python wins by inertia.
At my job I use Python because, well, at some point before I arrived one of the senior developers went on a jihad against Perl. :-)
I've read stuff about Ruby and while some things about the language intrigue me, it seems that any application you can build with Ruby can also be built with Python. If I'm going to learn another programming language in my Copious Free Time, I want to learn something really different from what I already know, not something that has pretty much the same features with different syntax and libraries. So Python wins by inertia.