What is the theme in Rumble Fish by S. E. Hinton?

Poverty is a major theme in Rumble Fish. Although Steve and Rusty James agree that their neighborhood is not "the slums," they note that it's "crummy." They live in a poor area. Steve's family is better off because his father apparently has a job, but Rusty James and the Motorcycle Boy have to scavenge, steal, and hope their father won't drink up all of his welfare check before they get a piece of it.