In 'mice and men' what is the purpose of crooks?

George and Lennie are obviously the protagonists in the novel, not Crooks. Crooks is there, mainly for the themes in Of Mice and Men. Steinbeck created the multi-dimensional character of Crooks to inform readers of how lonely and powerless the ranch workers were in 1930s America. Crooks is a prime example of this, especially as he is black. Instead of making loads of coloured workers, he created just one, so you can understand how isolated and lonely Crooks really is.