Why doesn't Crooks bunk with the other men?
He's been on the ranch much longer than the other men and has earned the privilege of getting his own room.
He's a black man and, even though slavery has been abolished by 1930, segregation is still common and legal.
His father and the boss are long-time friends so Crooks gets special treatment.
Crooks doesn't like the other men so he's requested to sleep with the animals versus having to sleep in the main bunkhouse.
Crooks is being disciplined for fighting in the bunkhouse so he has to sleep in the barn for an extended period of time.