I have a computer, an old laptop, that I mostly use as the foundation of my stereo system. It's just a basic system with a few servers (a web server and the music player daemon), and it doesn't have a running window manager. This configuration usually doesn't bug me: I connect remotely and the computer sits under the couch, but since my recent move I've not had a network connection at home and I've defaulted to playing music and managing the system from the console.
This works just fine for me. The virtual terminals aren't noticeably different from the terminal I get over ssh (as you would expect/hope), except now I have to walk across the room. The people who listen to music with me haven't yet been other terminal geeks, and so I've taken on the role of stereo whisperer. Until a friend looked over my shoulder and wanted to change the track. Using the console is sometimes (often) a slippery slope.
I realized immediately that this situation was much more conducive to learning to use the console than the kinds of introductions to using the console that I've typically written. The commands we used were very limited: the mpc program that acts as a simple command-line client to the music player daemon (mpd) and grep. We also used the pipe operator.
There are thousands of commands on most Linux/UNIX systems and remembering all of them can be a bit challenging. The console is a limiting environment basically you can do one thing at a time with it, and you don't have a lot of leeway with common errors. At the same time, there are a great number of programs and commands that a beginner has no way of knowing about or knowing when to use. Legitimately, the console is both too limiting and expansive to be quickly accessible to the uninitiated. Starting with a very limited selection of commands is way to break through this barrier.
The terminal environment is also very "goal-oriented." Enter a command to generate some sort of output or result and then repeat. At the end your system will have done something that you needed it to, and/or you'll learn something that you didn't already know. When you're just trying to learn, all of the examples seem fake, contrived, and bothersome because many people already have an easy way of accomplishing that task using GUI tools. Learning how the terminal works, thus, needs a real example, not just a potentially realistic example.
The great thing, I think, is that once you have a need to learn command line interaction, it makes a lot of sense even to people who aren't die-hard geeks: Commands all have a shared structure that is fairly predictable and inconsistencies are apparent. Perhaps most importantly the command line's interaction model is simple: input a command and get a response. Advanced users may be able to bend the interaction model a bit, but it is undeniably parsimonious.
It seems, in conclusion, that the command-line is easy to learn for the new user for the same reason it is beloved by the advanced. Ongoing questions, include:
If this kind of realization were to catch on, how might it affect interaction design in the long run? Might "simple to design" and "easy to use" move closer together?
Is there a way to build training and documentation to support users who are new to this kind of interaction style?