Exactly. Why isn't the current directory searched? Why isn't foo/bar searched for on PATH? Why is it possible for the user to accidentally remove system commands from PATH and lose access to them? Any system is confusing and surprising to users only familiar with another system.

And I've had very bad experiences in the past with languages/applications that presume to define a "cross-platform" abstraction that ends up just "not behaving how I expect a native app to". You can build a cross-platform wrapper on top of native behaviour (witness `shutil.which`) but you can't do the opposite.

Maybe there's scope for a section in the documentation that discusses how to use `subprocess` in a platform-agnostic manner. I'd be OK with that, although I'd want it to read along the lines of "these are places where Windows and POSIX behave differently" and not "here's some weird stuff Windows does that POSIX users need to be aware of" which was how your comment read to me.

Never mind, I think we can just agree to differ on this. It's not likely to impact this issue or the PR for it.