Being able to script a program is amazingly powerful, but I find the reason I like terminal-based programs is primarily due to the interface. The interface of a terminal program (both command-line and interactive) is the keyboard, which is a vastly superior input mechanism than the mouse for most things.

Any thought that goes into the interface of a terminal-based program goes toward the keyboard interaction; there isn't a GUI to think about. Because of this, terminal-based interfaces are usually much better than any graphical application.