Why is Carlson the typical lonely guy?

Carlson typifies the "lonely" guy because he lacks the forethought to think about anyone but himself. He's a nice guy, he's friendly, but he also can't undertsand the importance of Candy's dog, Candy's feelings, or even the loss George feels after Lennie's death. Can you imagine losing your best friend and having someone who knew you both watching you having a drink with a friend at the bar and asking, "What the hell..... is eatin' them two guys." Pure selfishness!