John Steinbeck had many problems plotting his novel. He wanted a story about the hard lives of itinerant farm workers (bindlestiffs). He decided to create two such characters and introduce them traveling around together, since he had to show how they lived on the road. He wanted them to share a dream of owning their own farm, so that they wouldn't have to live like tramps and work like slaves when they could find work.
But this raised one of his problems. It does not seem quite natural for two men to own a subsistence farm together. The common pattern since the agricultural revolution began in Mesopotamia was for a man and a woman to own a farm and raise children who could take over and support them when they grew old. (An excellent example of this kind of scenario is found in the novel Growth of the Soil by Noble-prize-winner Knut Hamsun.) Many people have asked about the relationship between Lennie and George. Some have wondered whether they were gay--which was certainly something Steinbeck did not intend.
Steinbeck realized he could not have two ordinary men who wanted to share a farm because it would look like a homosexual relationship. He thought of making one of them physically handicapped and the other his caretaker. But then they couldn't both be farm workers. So he went the other way and made one mentally handicapped but unusually big and strong.
This seemed to work out because Steinbeck intended to adapt his novella into a play. (See eNotes Study Guide "Introduction.") To make the adaptation simple, Steinbeck wrote most of the novel's espository material in dialogue, as can be seen in examining the text of the book. This enabled him to have George explaining everything to the dumb Lennie and then having to explain everything again, in the meantime explaining it to the reader and to the future audience of his New York play.
Steinbeck still felt he had to explain why two grown men wanted to own a farm together. He seems defensive about this. In Chapter Two, the Boss quizzes him:
"Say--what you sellin'?"
"I said what stake you got in this guy? You takin' his pay away from him?"
"No, 'course I ain't. Why ya think I'm sellin' him out?"
"Well, I never seen one guy take so much trouble for another guy. I just like to know what your interest is."
In Chapter Three, Steinbeck has Slim express a similar curiosity.
"Funny how you an' him string along together."
"What's funny about it?" George demanded defensively.
"Oh, I dunno. Hardly none of the guys ever travel together. . . . . It jus' seems kinda funny a cuckoo like him and a smart little guy like you travelin' together."
"It ain't so funny, him and me goin' aroun' together," George said at last. "Him and me was both born in Auburn. I knowed his Aunt Clara. She took him when he was a baby and raised him up. When his Aunt Clara died, Lennie just come along with me out workin'. Got kinda used to each other after a little while."
Lennie and George both get something out of their relationship. Lennie needs to be told what to say and do. George is "a little guy" and gets protection on boxcars and in hobo jungles by having a giant as his companion. Both get friendship. And John Steinbeck gets the advantage of having two characters talking to each other with the reader listening in. If Steinbeck had created a single itinerant farm worker he would have lost most of the drama his story contains, and adaptation to a stage play would have been nearly impossible.
There are three principal dimensions to George and Lennie's relationship: symbiotic, cultural and commercial.
The symbiotic: quite simply, they need each other. George wants to care for somebody, but does not have the means to marry and start a family. Lennie is his moveable feast, something he can tote around with him on his travels who will always need looking after. A wife and family would not be so totable, nor would George be able to stay in one place long enough to establish such a family. In this sense, Lennie has little inflluence: he's just another item in George's luggage, although he's very keen on the suitcase he's been installed in.
The cultural: becuase 0f the shiftless nature of work at the time in which the novel is set, having a partner was a mark of social solidity. It meant, at base, that whatever condition you got yourself into, there was somneone who'd stick by you,and who'd made a committment. Your partner was a walking, talking CV to your wholeness as a human being.
The commercial: with a partner as a CV, you were a more likely prospect for work that a lone drifter. You could stick at someting. Employers like that.