Pokemon Go still hasn’t reached China and now we know it’s not going to. China is banning the app because it may pose a threat to public safety. The decision announced by the State Administration of Press, Publication, Radio, Film, and Television says Pokemon Go can’t be allowed due to “national security” and “safety” concerns.
Another concern is that the game may pose a “threat to geographical information security.”
The game did result in quite a few absurd accidents (e.g. falling off cliffs) shortly after its release, so the public safety concerns are the easiest to understand.
Iran also banned Pokemon Go in August 2016.