...because it is definitely not the Safety stat. From time to time, my nation description says it's safe, despite my Safety score being one of the worst in the world.
I have a ridiculously high military, moderately high police force and no crime, so it must be why. That still doesn't make sense though, do you know why my Safety is so low? It's because the danger is not the citizens, but the authoritarian government, since it's a Psychotic Dictatorship. Anyone in my nation is definitely not safe from disappearing and waking up to a shark pool.
Basically, the safe keyword should be linked to the Safety stat instead of crime.