People keeping watch through the night are, of course, meant to spot things that happen around the camp. Occasionally the GM will have a night ambush of some sort planned, or perhaps a random encounter with some nocturnal beasts that are potentially dangerous. if not, then its usually handwaved with a simple "nothing happens" and you move on to the next day.
But consider how a watch session at a camp in a fantasy wilderness setting would really work. You'd constantly be on edge listening for cracking twigs, expecting giant spiders or worse to leap out of the inky darkness at any second. Any noise would trigger a rush of adrenaline and a spooked peering into the dark, trying to see what made the sound. Something as simple as a rat or a bat could easily trigger a full scale rousing of everyone and instant transition to battle mode.
Honestly, it's amazing that adventurers manage to get so-called "Long Rests" at all.
Commentary by memnarch (who has not seen the movie)
Ok, so I was half right. Maybe Luke just isn't feeling like talking? I wonder what he's doing in the cockpit. Maybe it's just a callback to the previous movie where Han had a similar "wander on in" moment. Heck, it would arguably make even more sense for Luke to reminisce for a bit as this would have been the place of his first look at outer space. Well, more sense to look like he's thinking about things anyway. I'm not sure if that sort of thing would flow well as a monologue in the movie at this point.
I'm still pretty sure that Luke's not actually going to steal the Falcon. But now it's like 85% sure instead of 99%. I suppose powering the cockpit up to fly away is an option, but a more likely reason is that it's really dark in here, and this is like the equivalent of flipping the light switch, right? Luke might look like a grumpy old man now, but he's probably not turned into a huge jerk about everything? He probably just wants to read his subscription to the Ahch-To Times and for the new folks to stay off his
Luke: While you’re busy spreading prion diseases, I sneak into the Falcon.
Chewbacca: I’m on guard. I’d notice him, yes?
GM: You’re occupied with the porgs. And Luke might be using Force Stealth?
Luke: Of course.
GM: <roll> He sneaks in unnoticed.
Rey: Seriously? You have one job here: to guard the Falcon.
Chewbacca: It’s Luke. What’s he going to do?
Luke: I power up the cockpit and steal the ship!
Luke: Just kidding.
Rey: No, do it! Teach him a lesson!