Jokes aside... it's so trendy to bash bash that it's not funny anymore.
Bash is still quite reliable for work that usually gets done in CI, and nearly maintenance free if used well.
I prefer python there, although we do test/deploy on Windows too, so it's nice to have a common python script for Windows and Linux CI. Not interested in making bash work on Windows or scripting in powershell. And although it's a lot more awkward to use python than bash for invoking subprocesses, it's nicer in most other ways.
Jokes aside... it's so trendy to bash bash that it's not funny anymore. Bash is still quite reliable for work that usually gets done in CI, and nearly maintenance free if used well.