The teens claimed CBP targeted them because they hadn’t booked hotels for their entire stay in Hawaii.
“They found it suspicious that we hadn’t fully booked our accommodations for the entire five weeks in Hawaii,” Pohl said. “We wanted to travel spontaneously. Just like we had done in Thailand and New Zealand.”
But, people haven’t been bringing money with them for decades now. They use payment cards.
But overall CBP looks at funds. If someone can’t afford their stay, they become suspicious.
EDIT: Adding, they ask how much people intend to spend or call banks to verify