The general workflow I'm finding useful is to generate a ton of simple logs, ingest all those logs into a SQLite database (that acts like a "data lake"), and then use the customized REPL to generate some charts (typically .png files), CSV, or ascii reports.
I could see using a REPL to generate a TUI, e.g., "run a query and generate your own `top`". This seems like it could be a lot easier than trying to generate a PDF, interactive Excel, or complex HTML report (which usually means a bunch of javaScript).
There's something about text interfaces that just fundamentally "flows" from most programming environments.