[polishdude20]

I wonder if it's to do with always focusing on the same distance. When doing a job where you're walking, your eyes are constantly focusing at different distances and taking in lots of information that's more rich than any website can give you.

Maybe constant screen time just tells your body "hey you can relax, nothing is around to attack you"

[hollerith]

Why would "hey you can relax, nothing is around to attack you" wear you out?

[polishdude20]

It signals to your body that you can sleep? So you stop producing whatever it is that makes you alert, attentive, energized.

[hollerith]

Sure, but if I slept or rested during working hours, I'd be more energetic in after working hours, not less.