Right, I'm often asked this about Oil [1]: Why do you want to write programs in shell?
That's not the idea of shell. The idea is that I write programs in Python, JavaScript, R, and C++ regularly, and about 10 different DSLs (SQL, HTML, etc.) And I work on systems written by others, consisting of even more languages.
I need a language to glue them together. A language to express build automation and describe deployed systems. Most big systems consist of more than one language.
Shell is the best language for that, but it's also old and crufty, with poor implementations.
When you program in shell, gcc, git, pip, npm, markdown, rsync, diff, perf, strace, etc. are part of your "standard library".
Update: also see the philosophy for structured data in Oil below: https://news.ycombinator.com/item?id=24083931