Your question about John Steinbeck's novella Of Mice and Men is a very good one. Steinbeck evidently wanted to write a story about the hard lives of agricultural workers in California, but most of his book is confined to a couple of indoor settings, a bunkhouse and a barn. The only exceptions are in the first and last chapters which take place at a campsite on a riverbank. If you refer to the Introduction in the eNotes Study Guide you will see that he planned to adapt the book into a stage play, and the play was produced in New York in 1937, the same year the book was published. This probably explains why the book itself is so short, why it lacks the panoramic scenes of men working in the fields which such a work seems to call for, and why so much of the exposition is contained, not in narrative prose, but in dialogue. Here is an example of exposition conveyed in dialogue when it might have been conveyed in prose:
He [George] took on the elaborate manner of little girls when they are mimicking one another. "Jus' wanted to feel that girl's dress--jus'wanted to pet it like it was a mouse-- Well, how the hell did she know you jus' wanted to feel her dress? She jerks back and you hold on like it was a mouse. She yells and we got to hide in a irrigation ditch all day with guys lookin' for us, and we got to sneak out in the dark and get outta the country. All the time somethin' like that--all the time. I wisht I could put you in a cage with about a million mice an' let you have fun."
The book could be quickly and easily converted into a dramatic script with the same dialogue and some of the action occurring either in the bunkhouse or in the barn. It is noteworthy that much of the action occurs offstage and is represented by sound effects, such as the sounds of men pitching horseshoes and the sounds of horses stomping their feet and jingling their harnesses. When Carlson shoots Candy's old dog he takes it outside, and after a while there is the sound of a single shot. The only signs of men working all day in the fields in the hot sun is the sounds they make splashing water as they wash themselves after returning from work.
The fact that George shoots Lennie is a quick way of terminating the story and the play. The same minimal stage set could be used for the opening and the ending. The stage would be dark. There would be an imitation campfire lighted by electricity and not much else except for a couple of bed rolls and a few cooking utensils. The play was obviously not intended to be an expensive production, but it was successful in New York, according to the eNotes Introduction (see reference link below).
California in the 1930s was a relatively small and unimportant state, with a population of around two-and-a-half million, as compared to over thirty-five million today. Steinbeck, regarded as a "regional writer," may have been more interested in getting his story and message to the center of power on the East Coast where the intelligentsia resided. His novella is just long enough to be converted to a stage play that would last two or three hours with an intermission halfway through.
The success achieved by Of Mice and Men, both as a book and as a play, gave Steinbeck the confidence to go ahead with a full-length, panoramic novel about the harsh lives of the working poor in his masterpiece, The Grapes of Wrath, published in 1939 with phenomenal acclaim.