[news.eclipse.platform] Why is it needed for java bean to implement prop

[d95776@xxxxxxxxx (hao)]

jface databinding framwork has provided a lot of help classes, such as 
BeansObservables and WritableValue. Why is it still needed for java bean 
to implement property change support, such as 

public class Message extends ModelObject {
..
}

public class ModelObject {

	private final PropertyChangeSupport propertyChangeSupport = new 
PropertyChangeSupport(
			this);

	public void addPropertyChangeListener(PropertyChangeListener listener) {
		propertyChangeSupport.addPropertyChangeListener(listener);
	}

	public void addPropertyChangeListener(String propertyName,
			PropertyChangeListener listener) {
		propertyChangeSupport.addPropertyChangeListener(propertyName, listener);
	}

	public void removePropertyChangeListener(PropertyChangeListener listener) 
{
		propertyChangeSupport.removePropertyChangeListener(listener);
	}

	public void removePropertyChangeListener(String propertyName,
			PropertyChangeListener listener) {
		propertyChangeSupport.removePropertyChangeListener(propertyName,
				listener);
	}

	protected void firePropertyChange(String propertyName, Object oldValue,
			Object newValue) {
		propertyChangeSupport.firePropertyChange(propertyName, oldValue,
				newValue);
	}
	protected void fireIndexedPropertyChange(String propertyName, int index,
			  Object oldValue, Object newValue) {
		propertyChangeSupport.fireIndexedPropertyChange( propertyName,  index,
				   oldValue,  newValue);
	}
}