The only really important thing about his departure is the fact that his leaving left space for George, who would then occupy his bunk. It is possible that if he had not left, that George would not have found employment on the ranch. Since Lenny is inseparable from him, he would also have not come to the ranch. This possibility, however, is not cast in stone.
George discovers a small yellow can in his box shelf when he prepares his bunk and is immediately sceptical about the conditions in the bunkhouse. He suspects that it is infested with lice, or, as he calls them, 'pants rabbits'.
Candy explains that Whitey, who had occupied the bunk, was a blacksmith and obsessively neat.
“This here blacksmith—name of Whitey—was the kind of guy that would put that stuff around even if there wasn’t no bugs—just to make sure, see? Tell you what he used to do—At meals he’d peel his boil’ potatoes, an’ he’d take out ever’ little spot, no matter what kind, before he’d eat it. And if there was a red splotch on an egg, he’d scrape it clean off. Finally quit about the food. That’s the kinda guy he was—clean.
Candy furthermore explains that Whitey would have bought the insecticide just to make doubly sure that his place was clean, even if there were no bugs. He tells George that Whitey had probably left the ranch because he could not stand the food and that made him want to move. No other reason for his departure is given.
Candy's explanation reads:
name of was the kind of guy that would put that stuff around even if there At meals little spot, no matter what d scrape it clean. Used ta dress up Sundays even when he was going no place, put on a necktie even, and then set in the bunk house. ”
“I ain’t so sure,” said George skeptically. “What did you say he quit for?”
The old man put the yellow can in his pocket, and he rubbed his bristly white whiskers with his knuckles. “Why . . . . he . . . . just quit, the way a guy will. Says it was the food. Just wanted to move. Didn’t give no other reason but the food. Just says ‘gimme my time’ one night, the way any guy would.”
It is therefore obvious that Whitey was eccentric and it is this idiosyncrasy which compelled him to leave the ranch.