Why does UMLObject derive from QObject, anyway?

The two signals declared in UMLObject are only connected to other 
SIGNALS in the classes derived from UMLObject; there are no SLOTS which 
use these signals, AFAICT. (I just opened the Umbrello project in Qt 
Creator and made extensive use of the "Find References to Symbol under 
cursor" feature...) And it seems that the automatic deletion facility 
offered by the parent-child relationships of QObject types is mostly not 
used, or not used correctly.

Is there any documentation that explains the reasoning for this QObject 
relationship? If the other derived classes were not QObjects, maybe it 
would be easier to implement proper copy and assignment which are 
disallowed by QObject (and more predictable memory management).

Of course, this applies mostly to the non-widget classes; we need the 
widgets for the diagrams and the rest of the GUI, of course. But the UML 
document objects could just as well be non-Qt classes, perhaps 
implementing the underlying data stores for different model types which 
the diagrams and views (list and tree views) could use.