I need the feedback indicating the state of the node (notebooks or tags) to free up a little of my memory. I want to be able to forget the state of the node and use this memory for my real work.
If I close the node notebooks or tags and I put my eyes back to the side menu after a while, I don't understand why my notebooks have been deleted. I need to use some of my limited brain time to remember that 1) it is a node, 2) that is closed and 3) I have to expand it. It is almost nothing but after a while it can erode a little of my concentration.
@tessus: If I have to use your metaphor, my precious real estate is my brain and I can only use it for a limited amount of time before it needs another break. And I'm sure my concentration capacity will deplete before your 4k screen will run out of pixels 
All this is just based on my feelings, but I have the intuition a lot of people are like me. It would be very nice if a designer come into this discussion.