BEIJING—On her first trip to China, 30-year-old Courtney Newnham from Portland, Ore., eagerly lined up at a street pushcart to buy a skewer of candied hawthorn berries, a traditional snack.

Then she realized nobody was giving the pushcart guy money. “Everyone was just scanning and walking away, and I was like, ‘Wait, what?’ ” she said. She left empty-handed.

China...