I suspect it has more to do with stringing together the inputs/outputs of multiple programs, which is outright painful in python. The syntax is terribly verbose (import subprocess, use subprocess.call, refer to a few enum values in the subprocess package, wire them together which requires a line of code rather than a character). Worse, pipes are tricky to implement correctly. It's easy to deadlock the python process by overflowing a pipe's buffer (wait for exit to read the buffer, buffer fills before subprocess exit, deadlock), so people who don't have an intimate knowledge of the underlying implementation will find themselves stuck with a bug they can't fix.

Compare this to a shell where the combination of &&, ||, and | can fit on a single line what would have taken dozens of lines of python.