Why can't North Korea travel with a mobile phone?

Mobile phones are absolutely contraband in North Korea, except for a few senior officials of the government and the army. Even ordinary Korean nationals can't hold it. Of course, foreign tourists are not allowed to bring it. Today, North Korea, like China in 1970s and 1980s, prohibits its citizens from contacting any information and ideas from the outside world. Even watching DVD privately and listening to foreign radio stations will go to jail, not to mention mobile phones.