bash is rarely the focus though, it really just costs 1MB in storage, which is nothing comparing to python,etc.

Well, usually I have to decide between „do I look up the magic incantation to install bash in this container and risk fucking up the layer cache“ or „do I modify this script to not use bash-isms and feel like I’m a Unix purist in the process“, and the answer is the latter usually

Just 1MB? That's most of a double-density floppy disk!

Nonetheless Bash is very frequently omitted in my experience.