- Shell scripting has simpler notations for I/O redirection.
- It is simpler to create pipelines out of existing programs in shell.
- Shell scripting reuses entire programs.
- Shell is universally available (on anything like Unix) - Python is not necessarily installed.
'Tis true that you can do everything in Python that you can do in shell; 'tis also true that there are things that are easy in Python that are hard in shell (just as there are things that are easy in shell but hard in Python). Knowing both will be best in the long term.