Lennie Small is the keeper of the dream. In his child-like naivete, he is convinced that possessing a ranch is in the realm of possibility. Upon seeing the Curley's wife dead, Candy bemoans,
"Ever'body knowed you'd mess things up...I could of hoed in the garden and washed dishes for them guys."
Candy realizes that he will probably be dead before he and George can save enough for a ranch, since he has to take on half of the price now. Without the monetary contribution from Lennie, the dream does not seem possible. The effect is much like that of children around Christmas time who believe in Santa Claus; they generate a faith in something outside of reality and make it magical for others too. As George speaks with Candy before leaving the barn to go after Lennie, he tells the old swamper,
"--I think I knowed from the very first. I think I knowed we'd never do her. He musta liked to hear about it so much I got to thinking maybe we would."
Once Lennie is gone, however, the magic of faith outside the real world is removed and the men are faced with the grim realities of the Great Depression. Truly, there is a significance to the name given to this period of history as people were both depressed and disenfranchised. With Lennie gone, George is faced with this grim reality of the era in which he lives as is Candy, and they lose faith in the American Dream of owning a small ranch.
George and Candy could not have made a go of it because Candy was badly handicapped. He only had one hand. He couldn't do farm labor but could only do sweeping and mopping and other such chores. Without Lennie, George would have had to do all the hard outdoor work. With Lennie, the ranch would have been manageable because Lennie was tremendously strong and could do anything he was told to do. He would also be an enthusiastic worker because he loved the idea of having independence and self-sufficiency. Candy had very little to contribute but a small sum of money. He would have become even more of a liability as he grew older.
The logical thing for George to do would be to find a wife, not some old man with one hand who would be doing the housework and a little gardening. George is young, strong, industrious, capable. He might be able to find a widow who owned her own farm and would be delighted to have a man to take over all the hard outdoor work (like the character played by Tim Holt in the 1948 movie The Treasure of the Sierra Madre). Or George might be able to find an unmarried woman who had a few hundred dollars saved up. After all, he only needed six hundred dollars to buy a little farm in those days. If he had a wife he would soon have children and be living a normal life on his own property. This was the common pattern all over America. I am reminded of Knut Hamsun's novel Growth of the Soil, a marvelous book by a Nobel prize-winning author. The protagonist developed some land in Norway and built his own house. It wasn't long before he had a wife to share the place with him and to share the labor.
Steinbeck makes a point of establishing that George and Lennie are exceptional in the fact that they travel around together and work as partners. Candy tells George about how the migrant workers are footloose and unpredictable. He illustrates his theme by telling about how one man just packed up and left because he didn't like the food. George and Lennie are getting jobs on the ranch because two men have just quit and moved on. They work for a while and then decide on the spur of the moment to collect their wages, pack their few belongings, and hit the road. Slim tells George essentially the same thing.
"Funny how you an' him string along together. . . . Hardly none of the guys ever travel together. I hardly never seen two guys travel together. You know how the hands are, they just come in and get their bunk and work a month, and then they quit and go out alone."
As Slim says, George already knows how the hands are. He has had plenty of experience living and working with men like these. So from at least three characters' points of view the reader is informed that the vast majority of these migrant workers are loners and drifters. Evidently it was Steinbeck's intention to preclude the possibility of George considering finding a substitute for his friend Lennie and going ahead with the project of buying a small piece of farmland with a house on it. Anyone else he took into the partnership might be likely to get bored and restless or quarrelsome and just go back on the road practically overnight.
There would be no future in a little subsistence farm. Three men living together would have to be philosophers to endure the monotony. They would have nothing to do but work, eat and sleep. Most of their food would come out of the soil. They might eat a chicken or a rabbit occasionally. The cooking would probably be pretty bad. It was very hard to obtain any cash money because everybody in the region already had fruit, vegetables, eggs and milk. They would have a hard time buying shoes or clothing. They couldn't afford paint for their wooden house. The fifty dollars a month they were getting working for others, plus room and board, might begin to look better than what they had as independent farmers. The dream that George and Lennie shared was like a lot of other dreams: it couldn't be examined too closely.
George would have Candy, but Candy was getting old and only had one hand. He could have become more of a liability than an asset. George was already growing tired of being Lennie's guardian and caretaker; he wouldn't have wanted another dependent. No doubt after Lennie's death George packed up and became another solitary drifter.
The reason I believe they do not get the ranch is because it was a dream shared between Lennie and George it was their dream. George thought of it but Lennie like a child keeps the dream going. It is like when you tell a child you are going somewhere and what you are going to do they count down the days and remind you of it always. So, when Lennie died there was no need to keep the dream alive, there was no one who could share the dream with george as Lennie had. George was like Lennie's dad and worked to make sure they had money for the dream, and Lennie as the child kept the dream alive. I believe this is what George needed too someone that needed him to dream like them.