I see this on two levels. First off, the comment "what the hell ya suppose is eatin them two guys" shows that the majority of people still don't understand the bond between George and Lenny. Even in the end, most of the men think the world is a dog-eat-dog world without room for human compassion.
Secondly, we get the feeling that this incident may soon be put behind all the men and it will be life as usual. Much like how George and Lenny can't go into hiding but must get to the next job, these men don't have time to dwell on what's just happened. They'll head into town, have a drink, and report to work in the morning.