Comment by zahlman

I should have mentioned one of the main reasons setup.py turns out not okay for people (aside from the general unpleasantness of running code to determine what should be, and mostly is, static metadata): in the legacy approach, Setuptools has to get `import`ed from the `setup.py` code before it can run, but running that code is the way to find out the dependencies. Including build-time dependencies. Specifically Setuptools itself. Good luck if the user's installed version is incompatible with what you've written.