What is the importance of the minor characters in Of Mice and Men

As in most novels the minor characters support the major characters, plot and theme. Check out the GradeSaver link below. Besides Lennie, George, Candy, Slim, Curley's wife, Curley, Crooks , the rest can be considered minor characters.

http://www.gradesaver.com/of-mice-and-men/study-guide/character-list/