Because updating layer combinations needs every tip it can get.
You know the drill. Create a layer and then update each LC one at a time: Choose the LC, set the lock and eye right, click update, choose next LC. Round and round. It's worse if the new layer is below the "page break" in the layer list and you have to scroll down to bring it into view. I habitually flick the scroll wheel to bring the layer name up, but not precisely, so it shows up somewhere in the middle of the list. Then when you switch LCs again, the layer list resets to the top, and you have to scroll again.
Here's the tip. If the highlighted layer is positioned at the very bottom of the layer list, it will stay put when you switch LCs. No further scrolling needed.
It's the little things. In the layer dialog, it better be.
