You might be wondering why we bother with SSH and typing stuff at the command line at all when Raspbian comes with a perfectly nice graphical desktop environment and a whole repository of GUI applications? Well, the first reason is that we need all the CPU power we can get out of the Pi for our projects. With the current graphics drivers for X (the graphics system), the desktop eats up too much of the Pi's resources and the CPU is more concerned with redrawing fancy windows than with running our mischievous applications.
The second reason is that of stealth and secrecy. Usually, we want to be able to hide our Pi with as few wires running to and fro as possible. Obviously, a Pi hidden in a room becomes a lot more visible if someone trips over a connected monitor or keyboard. This is why we make sure all our pranks can be controlled and triggered from a remote location.