Why did Luis's brother want to go to the store in the white neighborhood rather than the one in his neighborhood

This isn't really explained. Here is a quote:

One day, my mother asked Rano and me to go to the grocery store. We decided to go across the railroad tracks into South Gate. In those days, South Gate was an Anglo neighborhood, filled with the families of workers from the auto plant and other nearby industry. Like Lynwood or Huntington Park, it was forbidden territory for the people of Watts. My brother insisted we go. I don’t know what possessed him, but then I never did. It was useless to argue; he’d force me anyway. He was nine then, I was six. So without ceremony, we started over the tracks, climbing over discarded market cars and tore-up sofas, across Alameda Street, into South Gate: all-white, all-American.