The language is simple but sentimental, so the reader realizes that George and Lennie have a soft side.
Lennie asks George to describe the dream in chapter 1. Lennie has clearly heard this many times before, and George even asks why he doesn’t tell it himself. He says he might forget some things, and he likes the way George tells it.
George says that guys like them usually have no one and nothing, and just go from ranch to ranch. But they have a future, because George has Lennie to look after him and Lennie has George.
Go on, George! Tell about what we're gonna have in the garden and about the rabbits in the cages and about the rain in the winter and the stove, and how thick the cream is on the milk like you can hardly cut it. (ch 1)
The idealized vision of the future described by George is symbolized by the rabbits. Lennie likes soft things, and so having a bunch of rabbits around to pet is his dream. He just wants to be free.
Somehow the sentimentality fits. We can picture the dream with them. We want it for them. Yet we also know that it is only a dream.