I disagree that subprocess is complicated. Replacing the os.system() is really simple: http://docs.python.org/library/subprocess.html#replacing-os-...
I think people are just used to system(), particularly if they come from C.
I think people are just used to system(), particularly if they come from C.
The little part you link to starts off simple, sure, but then says "Calling the program through the shell is usually not required.", and proceeds to present a "more realistic example", leading to an immediate "WTF?" for anyone just learning of subprocess.
People who have been doing things the obvious way for years will not take well to a new mechanism that they don't understand the function nor implications of, and whose use is immediately discouraged by its own documentation.
99% of system() calls (regardless of language) will never be so adorned. It's used for quick hacks, rarely anything more. If the return code is checked at all, people only pay attention to whether it's something other than 0.