Why Python and why not shell scripting, Perl, Ruby, R or Java…? I think it is almost impossible to give an concluding answer. At the moment Python seems to be most flexible opportunity to use a wide range of GIS libraries and APIs as well as tons of Python libraries. Nevertheless is Python the language that you should choose if you want to develop something more fast and stable than for instant R. Additionally you can mix Python with shell, R and arbitrary other scripting languages.