If George refuses to accept the bunk, there will be no other place for him to sleep. He will have to quit. And if he quits, Lennie of course will quit with him. They will have to tell the boss they are leaving even though they have no wages coming, and they will have to explain why. Otherwise, George and Lennie could get in trouble with Murray and Ready, the agency in San Francisco that got them the jobs. In fact, they would have to head back to San Francisco and try to get assigned elsewhere.
Candy is solely responsible for keeping the bunkhouse clean. He could easily get fired if the boss believed he was not doing a proper job. The boss is already mad because he has been short two "buckers" for several days. It will take a few more days to replace George and Lennie. The boss wouldn't need much of an excuse for firing Candy. A worker with only one hand can't be of much use to him in any capacity. He is only keeping Candy on because he feels sorry for him and responsible for his injury. Furthermore, he probably gives Candy little more than room and board. But if he thought Candy was causing him trouble and making him lose money, he could use this as an excuse to get rid of him--whereas his real reason might be that he didn't want to employ a man who was getting old and only had one hand.
The boss is a bully with a bad temper. Earlier, Candy tells George:
"The boss gives him (Crooks) hell when he's mad."
"Well, he's a pretty nice fella. Gets pretty mad sometimes, but he's pretty nice."
The boss sometimes takes his anger out on poor Crooks, because Crooks is an aging black cripple who can't get any other job. This stocky little boss is just as likely to take his anger out on Candy and even fire him, especially if he suspected that the whole bunkhouse might have gotten infested with lice or bedbugs. That is why Candy is so anxious to convince George that the bunk is about as clean as could be expected after being slept in by countless drifters.
Much like his old dog, old "stoop-shouldered" Candy has just about outlived his usefulness. For,after having lost his hand in a machine, he has been relegated to sweeping out and cleaning the bunkhouse. So, when George, who is very particular about his accommodations, notices the can of insect and lice killer, he angrily demands, "Say. What the hell's this?" But, Candy remains calm and asks for the can, explaining that the previous occupant, a blacksmith was so cleanly that he kept such things around whether he needed them, or not. "Used to wash his hands even after he ate." Then, Candy elaborates on the obsessive cleanliness of the blacksmith, explaining that he would remove the eyes from the potatoes that he ate, and if there were a "red splotch" on an egg, he would scrape that off.
Clearly, Candy is insecure. When Carlson tells Candy that he will get rid of his stinky old dog, all Candy can do is look to Slim helplessly, "for Slim's opinions were law." The best that Candy can hope for is to live out his days on the ranch; this is why he becomes elated when there is the possibility of his joining George and Lennie on a farm.