While it is true that few of us are itinerant ranch hands who have a mentally challenged friend to take care of, Of Mice and Men by John Steinbeck is still popular because readers can still make a connection to the story.
The characters are familiar to us, despite the fact that their jobs are rather antiquated and unfamiliar to us. We do not know swampers on barley ranches, but we do know of people who are as unhappy as Candy is, feeling trapped and helpless because he really has no other choice but to stay where he is.
We know people like Crooks, who has a chip on his shoulder because he feels as if everyone is out to put him down (and many are) but is willing to open up just a bit when he realizes maybe everyone is not that way.
We have certainly met people like Curley: conceited but without the good to back up his bravado, jealous because he is insecure, pugnacious because he would rather start a fight than wait for someone else to start one with him.
And I am hopeful that we have all met someone like Slim, who is reasonable and honest, a true friend when we need one.
Notice that I did not mention George and Lennie, the central characters of the novella. We are struck by George's loyalty and Lennie's innocence, and we know what it is like to have a dream that, even though we keep talking about it, we know will never come true. Even then, it is not the characters as much as the relationships to which we relate.
The friendship between these two unlikely men moves us. They are nothing alike physically or mentally, but they share a dream. We admire George's loyalty to Lennie, especially since we know George could walk away from Lennie at any time and avoid all the trouble that seems to cling to them like lint, but he does not. We appreciate Lennie's bumbling innocence; and we know that, despite the results, all he really wants to do is pet soft things because he finds it calming.
We know that for some cruel and heartless people, shooting Lennie would be easy; however, we understand George's anguish over this decision.Though that final act does not look like love, we know it is, because we understand that Lennie would never survive in a world without George.
It is this relationship which makes this a relatable and timeless story, despite the modern reader's inability to connect with the specifics of the time, place, and language. We all understand, at least a little, how George feels when he says:
“A guy needs somebody―to be near him. 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, I tell ya a guy gets too lonely an' he gets sick.”
Oh yes, and it is still popular with students because it is short.