Modules written in pure Python (using the standard library) will mostly run on any of the 20 platforms that the Python (https://www.python.org/) website mentions. Each time you add a third-party module that relies on bindings to external libraries in other languages, you reduce Python's inherent portability. You also add a layer of complexity to fundamentally change the code by adding another language into the mix. Pure Python keeps things simple. Also, Python bindings to external libraries tend to be automatically or semi-automatically generated.
These automatically generated bindings are very generic and esoteric, and they simply connect Python to a C/C++ API using the method names from that API, instead of following the best practices for Python. There are, of course, notable exceptions to this approach that are driven by project requirements...
