our brains and bodies are lazy and efficient, do nothing long enough and the instinctive "screensaver timeout" kicks in, and you get bored, then loose alert attention. preventing this from happening for multiple hours is tiring and a skill which means it gets easier to do the more you do it
Or maybe the other way round! Master meditators could be great at piloting as well..
That said, one of the steps in being qualified to fly any given aircraft is having to occasionally get in the simulator and fly a "Kobiyashi Maru" type sequence of multiple compounding emergencies over and over again. You're being graded not just on being able to follow the checklists, but knowing enough about the aircraft to know what to do when multiple systems fail and the checklists contradict each other, or you're in a corner case where following a checklist blindly is a dumb idea.
In cases like these, being able to be calmly present in the moment is a very valuable skill.
Getting to a hotel to sleep takes a lot of time even after wheels touch ground - gotta taxi, follow SOPs, pass through security/immigration, travel to the hotel, and then actually fall asleep. Also, repeat in reverse to get back to work.