north-korean people don't have smartphone ?
North Koreans have access to an intranet, which is a restricted version of the Internet containing only sites created by government officials for informational purposes. As far as we know, no ordinary civilian in North Korea has access to smartphones or any other entirely free device.
Obviously the North Korean government doesn't have full connection with people who live there, so it's irrelevant to whether North Koreans should have access to banking. If North Koreans ever had access to the full Internet I hope loads of their hands would be on Bitcoin straight away. For all we know there could already be black markets building there.