This is especially applicable to input objects or those other objects that may not be sub-classes of the Input object but can be clicked on by the user. For example, Anchor objects.
The property yields the current state of the disabled setting for the receiving object.
A separate property to the object's disabled property is necessary because it might depend on the context in which an object is used and whether that context (such as a form or window) is disabled. The implication is then that all child objects within that context would be disabled too. It's also necessary because some objects are not members of the Input object family but can still be disabled even though they do not have a disabled property of their own.