The usual interpretation is that scripts glue together system commands that don't otherwise incorporate one another. This is tremendously useful and is by itself a huge advantage over GUIs.
But the second sense is that vast libraries of scripts keep developers bound to their previous UI promises. You don't capriciously change command-line options without raising all kinds of ire. I've seen GNU tools (tar comes to mind) in which options have been "deprecated" for decades, yet are still available. I seem to recall a very small number of cases where options had their senses entirely inverted, to much protest, and ultimately abandonment of those tools. In other cases you've got generations of programs which support backwards-compatible options with precursors: exim and postfix with sendmail, ssh with rsh, alpine with pine, off the top of my head. Developer headspace and script compatibility are valuable.
On that note, whilst I find the *BSD's extreme conservatism annoying myself, I can appreciate that it does lead to increased consistency over time as compared with GNU userland.
There's also a lot of text based tools that are designed to be used as part of a script and don't provide much functionality in themselves - the philosophy of do one thing (and do it well). GUIs tend to be designed to provide the entire functionality that's wanted and little thought is given to them being used as part of a toolchain.
If someone makes a GUI that does specifically what you want, you're in luck. If not, you're S.O.L.
With CLIs, you can almost always find some way to string things together to get what it is you want.
The hard case is working in domains which aren't inherently textual: graphics, audio, video, etc. Even there, you can often get much more accomplished from the terminal than you'd think, though setting up the process can be challenging at times. Not so useful for one-offs, but invaluable for repetitive processes.
The usual interpretation is that scripts glue together system commands that don't otherwise incorporate one another. This is tremendously useful and is by itself a huge advantage over GUIs.
But the second sense is that vast libraries of scripts keep developers bound to their previous UI promises. You don't capriciously change command-line options without raising all kinds of ire. I've seen GNU tools (tar comes to mind) in which options have been "deprecated" for decades, yet are still available. I seem to recall a very small number of cases where options had their senses entirely inverted, to much protest, and ultimately abandonment of those tools. In other cases you've got generations of programs which support backwards-compatible options with precursors: exim and postfix with sendmail, ssh with rsh, alpine with pine, off the top of my head. Developer headspace and script compatibility are valuable.
On that note, whilst I find the *BSD's extreme conservatism annoying myself, I can appreciate that it does lead to increased consistency over time as compared with GNU userland.