There's something nice about riding on the really long voyages in the deep dark. One you pass through light speed between jump gates the boat smooths her ride and becomes quiet except for the CO2 scrubbers (which are the sound of life itself so you get used to it the way to get used to crickets at night).
It's true you can't go out in the sunlight. The outside is cold. There's no air.
There's a piano in the crew's "den". Along with the completely expected foosball table and "L"-shaped couch. When you're off of watch and a couple months in it can be relaxing to sit in a deep comfy chair and read while your 3rd mate studies for her engine exam at the desk in the corner.
"It's not boredom, it's relaxation" as my old Captain used to tell me. He would suck on a dry pipe, just to get the taste in his mouth. Any smoke on a interstellar boat like this and the alarms would go completely insane calling the entire crew out to either suppress the fire or abandon ship entirely. Sometimes both.
So the smokers would use little vaporizers instead.
The ship's cat, Molly, would stare out the window as though the comets were fluttering moths. Counting them as she licked her lips. Nobody closed their cabin doors all the way because Molly liked to patrol the ship, checking on each person at his watch, and to curl up at the feet of a radioman on break.