I mean doesn't need to be a screen. A book, music, small puzzle, etc. Something to keep your mind engaged. When you aren't mentally engaged with something it's easy for some people to start worst case scenario thinking and induce panic attacks which aren't ideal to have in general let alone on a plane.
Same reason some people can't sleep in silence.
Daydreaming seems to be a viable method though. Keeps your mind engaged and doesn't require anything. Also "most" people won't start worst case scenario thinking. Of those even, "most" of them won't induce a panic attack. However, if you do fall into that small percentage, absolutely, do what you need to keep your mind engaged and actively pursuing a healthy line of thought.
And "travel experts" are who we should all go to for the psychological evaluation of this method of decompression. And by "travel expert" they mean some guy that sits in a chair at their job and not someone whose job is to actually travel.
Same reason some people can't sleep in silence.