It is true that at the moment there are no wild Nidoking. This is not to say that they never appear in the wild; it is simply that the average lifespan of a wild Nidoking is about one year before they are killed in battle. It is a good thing for all of us that they are. Nidoking are great pillagers, great barbarians, a desperate and successful gasp of wild pokemon pushing back against the march of human civilization.
When a stone falls from the Moon to the Earth and a wild Nidorino finds it, they walk through the tall grass at night attracting followers by the simple fact of their existence. After evolving from Nidorino, Nidoking become kings in the old sense of the term – not solely by birth, but also by valor, winning their subjects' esteem so they can lead them into war, and growing their army with every victory. When a human stumbles upon it and escapes alive, or when one has gathered a sufficient pokemon force, they lead armies to descend on nearby towns. When they reach one, Nidoking personally crush buildings by using Earthquake and command their troops to kill every human they find. Some of these attacks have entered the history books, typically as among the most dire challenge a city or nation has faced, the kind which makes men pledge loyalty to their old enemies in a desperate hope for survival.
Others only enter the archaeological record, provided the pokemon have grown peaceful enough with time that the archaeologists can find it. Not all wilderness has always been that way.
