I made my case explicitly, and it's about technical limitations of CPython that can (and, at some points WILL) be overcome. PyPy is a step in that direction, though not mature yet.

Python, in the form of the standard and most used implementation for scientific, technical etc programming, CPython, DOES add integration requirements.

It necessitates the use of C/Swig/Cython etc extensions for performance critical stuff. And it necessitates it, not because it puts a gun in your head or says so in some contract clause, but in the pragmatic way, that people find it's not fast enough for their needs in pure form.

That's why all the popular related Python projects are not written in pure Python, but in C/Fortran/et al (NumPy etc).