You can of course do everything through a GUI. Windows' Find Files (from XP and earlier) is a somewhat GUIsh equivalent of the command you typed.
Now, why do UNIX (and Linux) users like shell? Because you can take the output, feed it into another program, and get different output. For example:
find | grep burek
These are two commands,
grep, one feeding the other.
find lists all files in current and all child folders, one per line, and
grep prints out only those lines that contain
Now, there are other, more complex things, such as:
ls -R | sort | uniq
ls -R lists files in current and child folders, and
sort sorts the output.
uniq then gives us only unique lines.
Now, while you can code all this into a GUI, you can quickly do such tricky stuff with command line that you can't ordinarily do with GUI unless you go write your own. In which case, it's faster to just type it into command line, isn't it?
Bottomline: If you ask this, you don't need it. Command line is useless for you as a regular user. Command line is however great for sysadmins, for developers, and those who want to mess around with their computer in a fast fast fast way.