Most people in the western world wouldn't think twice before plugging in a found USB stick into their own computer because they are curious, people simply don't know the risk. I'm sure even fewer people in North Korea know basic computer hygiene.
Most computers in various places like hospitals, veterinarians, shops, gyms and more all have exposed USB ports where it'd be trivial to plug something in when the clerk/assistant is looking the other way, just as another example.