This post really is addressed to Windows users having a hard time coming to terms with Ubuntu.
The command line interface (CLI, the ability to write commands directly into a terminal window, accessed for example via Applications -> Accessories -> Terminal) is a concept that pre-dates Windows as it was the main means of interaction with DOS or CP/M computers - here I show my age.
Linux and Ubuntu have maintained the CLI as a means of interacting with the computer. At least one generation of computer users have managed to communicate with their computers exclusively through Graphical User Interfaces (GUI) as provided by Microsoft and Apple - by pointing the cursor onto icons or keywords and by clicking the mouse. These GUIs have indeed made it simple for everyone to deal with computers, including pre-school infants. However much has been lost in terms of understanding how computers work. Indeed, many people don't care to know, and as long as they can do their job through good use of their software applications, they do not need to know.
However, for the curious, the CLI gives an insight into the operating system. It is rewarding, even if the Linux commands take a while to learn. The result is a more creative interaction with the computer and a sense of being in control.
Without a CLI, it is tedious to explain to a GUI user how to repair, modify or improve their computer, whereas a CLI command can be easily cut and pasted into a Terminal with immediate results. Anyone can easily and precisely report on the status of their computer by pasting the output of a CLI command. Communication between computer users is greatly improved.
The main point of this post is the following. Many praise Ubuntu for the great user community providing support and education. This is not found in GUI communities. I believe that the thriving forums in Linux and Ubuntu which give great depth to the support each one of us benefits from is largely due to the existence of the CLI, which makes communication so much easier.
If Ubuntu is gaining popularity, it is to a large extent due to the existence of our on-line communities. Their responsiveness, expertise and enthusiasm owes much to the CLI.