This plugins must be used from other plugins.
The user has no direct interaction with it.
For example its used in the archive/extract, create torrent process.
Something similar is implemented in filemanager/fileupload to show the output in the command console.
Also makes the rtorrent processs execute the commands (rm, cp, read write files, etc) since its running from the shell user it has the right permissions (enhancing security).
Without this important feature all user data should be readable and writable by the www-data/apache user which makes a big mess because data is written with the web user id (making data managing from ftp impossible), and a user could access other user's data. (this is one scenario,there are many).