But maybe a better question is why a "government" is necessary to have a passport at all? How many people who are alive today chose the government they live under? Is it perhaps 1% of the people? I certainly did not choose this oppressive government that protects the rich and humiliates the poor. Why should governments have such control over international travel at all beyond what they permit at their own borders?
Recall, a passport is identity and a request for courtesy, combined with an implied third meaning: which is the right to travel internationally. Why not have another, presumably international, body, certify the identity of a person and negotiate by treaty (1) the right to travel? Maybe the UN could do this and actually be good for something beyond getting their diplomats immunity from traffic tickets in NYC.
1. So far as I know treaties are made by sovereign countries and their descendants (e.g. when Soviet Russia picked up the treaties of Imperial Russia). So is the UN allowed to make treaties of this type? What is funny about this question is that I do not have a clue what the answer is, but I suspect the answer is "its complicated".