Command line applications (CLI) are often the core tools for automating tasks, such as deploying production applications, running tests, building reports, migrating data, DevOps, and the list goes on and on. If you find yourself doing the same things over and over again, chances are you can automate those steps with a script and save yourself a lot of time.
A bad CLI can easily discourage users from interacting with it. Building successful CLIs requires attention to detail and empathy for the user in order to create a good user experience. It is very easy to get wrong.