My favorite explanation is that in Indonesia, everyone is treated as family, so there's no need to nitpick over surnames. If I smile, most Indonesians will smile back. Indonesians address strangers as "Brother", "Sister", "Father" and "Mother". The forms of address for "Sir" and "Madam" are literally "Father" and "Mother", respectively. Indonesians are extremely inclusive and tolerant of people. Doors to most traditional homes are open to any and all visitors. I've never needed to plead for help when I needed it. Somehow, someone would always offer directions if I was lost, food if I looked hungry or a place to stay if I was homeless for the night.