Choice is a privilege you rarely have in a day to day job. Bash most of the time is already there and you have to live with it.
Also, I've been forced to work on a huge SCons based project and I guarantee python can make your life quite miserable when used for something it's not supposed to.
I'm not suggesting you build a a whole build system with python (which is basically bazel and it seems to be good enough for google.)
A lot of originally little automation/dev scripts bloat into more complicated things as edge cases are bolted on and bash scripts become abominations in these cases almost immediately.
Also, I've been forced to work on a huge SCons based project and I guarantee python can make your life quite miserable when used for something it's not supposed to.