I'm not a supporter of N. Korea, but let me play the devil's advocate. Kim Jong-un is familiar with western customs and this photo op is almost certainly propaganda in his campaign. Most North Koreans are not familiar with western customs. It is a ENTIRELY western custom to smile in photographs. In fact, many believe it's disrespectful to do so in deep parts of India, China, middle East, and I presume East Asia. Reference the number of photos of my parents and grandparents and family in the village that are super serious in their wedding photos.