Here's a setup.py that includes an interactive prompt, and thus breaks all ability to do automated installs! https://github.com/pypa/pip/issues/2732

Here's a setup.py that cannot even be imported unless another package (numpy) is already installed: https://github.com/scipy/scipy/blob/master/setup.py

I've seen setup.pys that read random files from the filesystem. I've seen setup.pys that shell out to random system commands that may or may not be installed. It's just a horrible format for what it's trying to accomplish.. because it's not a format! It's a programming language.