Why Ubuntu uses the Indicator Applet?
It loses a lot of usability, why made it when Gnome already have one?
Example
Without indicator applet:
Application is in the icon tray
Left click opens the application window
Right click shows a menu related to application
With indicator applet:
Application is in the icon tray
Left click shows a menu with a few options related to application
Right click shows a menu related to "indicator applet"
This means it takes 2 clicks to show the application main window,
while before it need only one.
Why make something that already exists and is useful?
Why change for something that no has usability?
Best Answer
Design justification and analysis is available here.