It allows easy management of each application's volume and output. GNOME's system menu only features a volume slider for the currently selected audio output. More functionality is found in Settings > Sound. Not only is this inconvenient, it lacks any way to change audio output on a per application basis. You can only select one output at a time, for all applications. To change each audio outputs per application in Gnome, software like PulseAudio Volume Control is required. This is not convenient and annoying, since it's easy to accidentally adjust the wrong settings by scrolling through them in PulseAudio.
I am looking for a way to implement a KDE-esque audio control for Ubuntu/GNOME system menu.