Crooks is different from the other men because of his physical impairment and because of his race. He does not have the same option to move from one job to another. All the other workers are temporary itinerant drifters. George describes them to Lennie in the opening chapter of the story.
"Guys like us, that work on ranches, are the loneliest guys in the world. They got no family. They don't belong no place. They come to a ranch an' work up a stake and then they go inta town and blow their stake, and the first thing you know they're poundin' their tail on some other ranch. They ain't got nothing to look ahead to."
Since the white workers have to be on the move, because of the nature of agricultural work in California as well as because of their own shiftless characters, they don't want to accumulate things they have to carry when they are walking, hitchhiking, or hopping freights. They all have a bedroll, a safety razor, a toothbrush, and a few other necessities, but not much else. It is probably just as well that they don't carry anything of value, because it would either get taken away from them by stealth or by force.
But Crooks has to stay in the same place, so it doesn't matter how much property he accumulates. Most of it is junk he has found in the trash or somebody has left behind because he didn't want to be encumbered. Crooks feels lucky to have a job. He would have a very hard time getting another job on a ranch, and he would have a very hard time even getting to another ranch because of his physical condition. Even if he did go elsewhere to ask for a job, he would get turned down because of his race.
Candy is in a similar predicament. He has only one hand and can't do field work. The boss keeps him on as a "swamper," a janitor, partly out of pity and partly out of guilt. Candy would have a very hard time getting another job, and he knows it. That is why George and Lennie's scheme to buy their own place appeals so much to Candy and why he is so disappointed when it falls apart.
The stable buck, as he is called, lives in the harness room of the barn, having worked on the ranch for years; Crooks is originally from California, so he has not moved far. Being black and having been injured, Crooks probably figures that he should just stay where he is with the job that he has. Since he has lived on Curley's father's ranch for some years, he has been able to accumulate a number of personal possessions. Also, because he is marginalized and cannot toss horseshoes. play cards, gamble, or visit with other men on the ranch, Crooks has acquired some magazines and some books which he has probably read and reread, along with a dictionary, all of which stay in his room in order to fill the vacancies of friends.
Crooks possessed several pairs of shoes, a pair of rubber boots, a big alarm clock and a single-barreled shotgun. And he had books, too; a tattered dictionary and a mauled code of the California civil code for 1905. There were battered magazines and a few dirty books on a special shelf over his bunk. A pair of large gold-rimmed spectacles hung from a nail on the wall above his head....
When Lennie appears in the doorway, it is as though the barn has been invaded because Crooks is not used to company. In fact, he adopts an offensive tone and lets Lennie know that he is not welcome. However, the child-like man is too naive to understand the rejection.
Around this era it was difficult for African Americans to get stable employment and since Crooks is injured as well it is even more difficult for him to find any other type of work. So him being able to gain so many personal things is a result of him accepting a work life style at the ranch because he has few options. There is also the fact that Crooks is segregated from the rest of the workers because he is African American. So it's quiet natural that he accumulates so many things to preoccupy is time.