Attention gets tired. Not just when we are suffering through a boring lecture or listening to a rambling relative but pretty much all day, every day.
Wikipedia has some nice technical jargon..”.. overuse of the brain’s inhibitory attention mechanisms, which handle incoming distractions while maintaining focus on a specific task.”
I think this translates to “you get bored” (I also get lazy.)
Attention is a form of energy and that energy has to come from somewhere. Humans are energy generators, converting food, light and air into actions and thoughts so attention must be converted food, light and air. What do we convert attention into?