Chris's parents, Billie and Walt, reveal throughout the novel that they are people with conventional moral and social views, who have never deeply questioned the norms and values of US society. This sets them apart from Chris, who confuses them.
Billie shows her conventional morality when she says.
“Chris didn’t understand how people could possibly be allowed to go hungry, especially in this country,” says Billie. “He would rave about that kind of thing for hours.”
Billie unconsciously diminishes Chris's concerns when she uses the term "rave" to describe his speech, characterizing it as lunatic, and when she says "that kind of thing" dismissively, as if social justice concerns must be handled with tongs.
Billie shows her conventional, risk-averse, middle-class American social values when she says:
“I just don’t understand why he had to take those kind of chances,” Billie protests through her tears. “I just don’t understand it at all.”
Like most Americans, Billie places a high premium on security and comfort. She doesn't comprehend that Chris felt most fully alive when taking risks and challenging himself to get out of his comfort zone. She didn't understand that risks were part of his spiritual quest, a way to expand his soul and gain greater wisdom.
When Walt describes Chris's quirks with racquetball, he shows that he doesn't understand how Chris would value playing for its own sake more highly than becoming more competitive so as to be a winner:
He was very, very quick and had a lot of power; but when I suggested he work on the gaps in his game, he refused to listen.