For Steinbeck, the bank serves as the complete moral antithesis to the small farmers: large, imposing, austere, and machine-like, that bank is an institution without feelings or remorse. Even the men who work at and own the banks are referred to as “slaves” of the banks, which are “machines and masters all at the same time.”
Steinbeck’s book is about the hardships faced by poor Western-American farmers during the Depression Era. His characterization of the bank allows him to juxtapose its lifeless, calculating presence against flesh-and-blood human beings. For example, a group of squatting tenant men have a conversation about what the bank is and why a farmer shouldn’t borrow money from it. One says that a man can hold on to his land and grow crops until they fail, and then he must turn to the bank for help. He continues,
“But you see, a bank or a company can't do that, because those creatures don't breathe air, don't eat side-meat. They breathe profits; they eat the interest on money. If they don't get it, they die the way you die without air, without side-meat. It is a sad thing, but it is so. It is just so.”
This description of the bank as a lifeless institution reinforces how antithetical its existence and way of sustaining itself are to the farmers who need its support. The bank doesn’t breathe, doesn’t eat meat. It is a completely artificial entity, dehumanized to the point of abject caricature. The point here is that real, breathing, common men and women depend on the bank to issue them loans so that they can keep their farms afloat and continue to feed themselves. Even thought the bank requires certain things to survive, it does not suffer the threat of death the same way a poor farmer does, making it a pure representation of evil.
This representation of the bank as something completely lacking humanity is reinforced later when the tenant men keep repeating that “the bank isn’t like a man” and “the bank is only made of men,” but is not actually one of them. The Grapes of Wrath has a lot of imagery relating to the nature and society of the American West. Imagery about the bank reinforces in the reader’s mind how unnatural and strange it really is.
Later in the story, when Thomas is talking about how much money the Farmer’s Association allows him to pay employees working his land, he reveals that the organization is owned by the bank. The bank forced employers like Thomas to drop their payments from thirty cents to twenty-five cents per hour. Thomas would like to pay the workers more, because his laborers were strong and reliable. Thomas’ rage signifies how callous and unforgiving this bank, a disembodied, money-collecting parasite, was when deciding how much money America’s poor farmers were worth.