Why does Crooks decide at the end of the chapter not to follow George and Lennie to their dream farm

Which two elements does this excerpt from a christmas carol by charles dickens contain? "a small matter," said the ghost, “to make these silly folks so full of gratitude." "small! " echoed scrooge. the spirit signed to him to listen to the two apprentices, who were pouring out their hearts in praise of fezziwig: and when he had done so, said, "why! is it not? he has spent but a few pounds of your mortal money: three or four perhaps. is that so much that he deserves this praise? " "it isn’t that," said scrooge, heated by the remark, and speaking unconsciously like his former, not his latter, self. "it isn't that, spirit. he has the power to render us happy or unhappy; to make our service light or burdensome; a pleasure or a toil. say that his power lies in words and looks; in things so slight and insignificant that it is impossible to add and count ’em up: what then? the happiness he gives, is quite as great as if it cost a fortune." he felt the spirit's glance, and stopped. "what is the matter? " asked the ghost. "nothing particular," said scrooge. "something, i think? " the ghost insisted. "no," said scrooge, "no. i should like to be able to say a word or two to my clerk just now. that's all."