The Linux foundation is one of the few open-source organizations that actually has significant money behind it (Mozilla is the only other one I can think of). PyPI moves hundreds of petabytes of data per year and a lot of orgs are simply not prepared to scale to that size. Without Fastly's support, the PSF wouldn't be prepared, either.

So it's more than a little annoying to see that resource wasted. Setuptools is one of the most downloaded packages, largely due to issues with the design of Pip. Numpy by my estimate accounts for over 10% of download volume by itself (it's both very popular and very large), and ships basically an entire development environment (including multiple test suites and patches for Setuptools) for both C and FORTRAN extensions, along with many megabytes of advanced math libraries, to clients who mostly don't need any of that. Most packages could be considerably smaller if the standards supported LZMA compression (which is already in the Python standard library). The metadata formats are awkward, both wasting space and failing to prevent downloads of package versions doomed to fail installation.