> To this day the default packages carried by Debian and Mac OS X (the two operating systems I use) are 2.x, so there is little incentive to upgrade most libraries.
Debian Python maintainer is not very good at his job: http://lwn.net/Articles/496335/ Be grateful that you even have Python 2.7. Also, a quick Google search shows that MacPorts has packages for Python3.
> On to the subject of the non-rivality with JavaScript: the PyPI has currently 29444 vs 26256 for npm
You are comparing a "batteries included" language with one that doesn't have a standard library.