LayoutRebuilder.Rebuild called text is outside viewable area of ScrollRect

Is there a reason why LayoutRebuilder.Rebuild() is getting called when an object (text for instance) is outside the viewable area of a ScrollRect?

In Unity 5.2.2, while the object (text) is inside the viewable area of the ScrollRect, there is no call to rebuild the layout but as soon as the object is outside the area, the calls begin.