Let’s give you a real world example.
About 15 years ago I worked on porting a large system written in C from Unix to Windows, it was about 3 million lines of code. To give you some idea of scale, it took over 24hr to compile on some of our unix systems (RS6000), windows could compile the system in about 4hrs.
(We also had 2 million line of code in our own interpreted language, but decided not to use our language for the build systems as it was never designed for file processing. Also we needed a build system to compile the C code that implemented our language.)
At the time the build system was written in a mix of shell scripts and make files, these were not portable to windows – therefore we decided to write our own build system.
We could have used C, however we decided to use python, there was few reasons. (We also rewrote our source code control system in python at the same time, this is was very intergraded with the build system, so object files for checked in modules could be shared by developers.)
Most of our code could be built with a few simple rules (only a few thousand lines of python for all platforms, Windows, VMS, and 6 versions of Unix) that were drived from the naming conventions of the files.
At the time RegEx was not very standard between C systems on different platforms, Python had built in RegEx.
A few modules needed custom build steps, Python allowed class files to be loaded dynamically. We allowed a custom class to be used to build a module (lib), based on having the python file with a magic name in the folder. This was the killer reason to use python.
We considered Java, but it was not shipping on all the platforms at that point.
(The UI for our source code control system used a web browser as that was portable across all the platform. This was 6 months before we had a internet connection. We had to download the browser over X25!)