Taking e.g. Python as a good example of a modern scripting language, it has the option of reading a program (as opposed to input data for the program) from stdin. The REPL is the obvious use case where stdin is a terminal, but it's also designed to handle the scenario where it's not a terminal.
What use cases are there for reading the program itself from noninteractive stdin?
(The reason I ask is that I'm working on a scripting language myself, and wondering whether this is an important feature to provide, and if so, what the specifics need to look like.)
If you want to execute code generated by some tool it could be useful to be able to pipe the generated into your interpreter/compiler..
Simply support it ;) Checking if stdin is a tty or not is not hard anyway.
Script from stdin use case