The Python implementation that we are using is a C-based implementation of the Python interpreter. NumPy is specifically for this C-based Python implementation. This implementation of Python comes with a C-API, which is the backbone of the interpreter and provides low-level control to its user. NumPy has further augmented this by providing a rich C-API.
Writing functions in C/C++ can provide developers with the flexibility to leverage some of the advanced libraries available in these languages. However, the cost is apparent in terms of having to write too much boilerplate code around parsing input in order to construct return values. Additionally, developers have to take care while referencing/dereferencing objects since this could eventually create nasty bugs and memory leaks. There is also the problem of future compatibility of the code as the C-API keeps on evolving; hence, if a developer wants to migrate to a later version of Python, they may be up for a lot...