Here are lines from the men in "Of Mice and Men" that express the terrible alienation of itinerant men. Steinbeck was most concerned with the importance of brotherhood as a means of giving meaning to the lives of lonely men who are helpless by their isolation:
'I ain't got no people,' George said. 'I seen the guys that go around on the ranches alone. That ain't no good. They don't have no fun. After a long time they get mean. They get wantin' to fight all the time.'
'Yeah, they get men,' Slim agreed. 'They get so they don't want to talk to nobody.'
'A guy needs somebody--to be near him. He [Crooks] whined, 'A guy goes nuts if he ain't got nobody. Don't make no difference who the guy is, long's he's with you. I tell ya,' he cried, 'I tell ya a guy gets too lonely an' he get sick.'
It is because they are so lonely that George and Lennie come together as brother in the dream of having a place. They look out for each other, protecting, looking out for the other's best interest. (See the quotes from the above post.)