Explain the meaning of the closing lines of the story. What do the lines reveal about Curley and Carlson?

The fact that Carlson can wonder what's "eatin" George and Slim is proof of his hardened status. He and Curley are so insensitive to the humanity surrounding them that they've lost the ability to show empathy..... in fact, they can't even see the need to fake it. They think about themselves and only themselves.

Curley and Carlson looked after them. And Carlson said, "Now what the hell ya suppose is eatin' them two guys?"