I prefer to spend most of my time sitting down by myself and thinking, so it's definitely not a matter of unplugging, nor is it a lack of stimulation.
For me, it's almost always that I'm exhausted and basically unable to be physically comfortable. When I have 10+ hour flights with layovers it feels like enhanced interrogation: I'm prevented from getting any significant amount of good sleep, and I'm forced to be in a kind of sitting stress position where I can't get comfortable and I can't sleep. Forget about reading, I'm just not capable of doing it.
For me, it's almost always that I'm exhausted and basically unable to be physically comfortable. When I have 10+ hour flights with layovers it feels like enhanced interrogation: I'm prevented from getting any significant amount of good sleep, and I'm forced to be in a kind of sitting stress position where I can't get comfortable and I can't sleep. Forget about reading, I'm just not capable of doing it.