Why is there extra wrapping of components?

cscooper

I see this a lot in online code - somebody needs a checkbox in a table, and they define their delegate like "matryoshkas":http://en.wikipedia.org/wiki/Matryoshka_doll:
@Component {
id: checkBoxDelegate

Item {
    CheckBox {
        anchors.fill: parent
        checked: styleData.value
    }
}

}
@

What is the benefit of this over a more simple definition:
@CheckBox {
id: checkBoxDelegate
anchors.fill: parent
checked: styleData.value
}
@

And it's not just people in the interwebs, the Qt documentation does the same thing (in http://qt-project.org/doc/qt-5/qml-qtquick-controls-tableview.html )

@
itemDelegate: Item {
Text {
anchors.verticalCenter: parent.verticalCenter
color: styleData.textColor
elide: styleData.elideMode
text: styleData.value
}
}
@

Why the extra layer of "Item" there? Why not just:

@
itemDelegate: Text {
anchors.verticalCenter: parent.verticalCenter
color: styleData.textColor
elide: styleData.elideMode
text: styleData.value
}
@

Thanks,
Chris