Why is Tom impatient with the gas station attendant in Chapter 13 of The Grapes of Wrath?

Tom feels that the man is being unfair, initially, then grows frustrated with the man's repeated question. 

As a refrain, the attendant asks what the world is coming to. When Casey offers an honest attempt at an explanation, the man simply repeats his question again. It is at this point that Tom speaks to the man in anger. 

Angrily Tom tells the attendant that although he asks that question, he, like many others, doesn’t really want to know. Tom warns him that he too will be affected and driven out by the big company gas stations. The man admits he has been considering leaving, and the family drives on.

Tom repents of his venom a bit when he realizes that the man is as poor as the people he questions. The attendant is at a loss and at a disadvantage financially, like the people moving west, but Tom is annoyed that he would continue to ask the question that he does not want to answer. 

Tom has a similar enounter later with a one-eyed man who laments over his pathetic state and does not seem willing to improve that state.