Welcome to Fluther.
It’s a good question. If you look into the history of passports and visas, you’ll find that they’re really just a 20th century invention – for commoners like most of us. At one time, before the advent of photo identification and mass data storage and regulation, passports and visas were issued to a government’s diplomats to identify them as bona fide representatives of the government to the foreign government to which they were sent. In other words, the French ambassador to the United States would carry a passport to Washington, DC, to identify himself and prove that he was indeed the representative of the government of France, while French citizens simply boarded ships and traveled here, there, everywhere.
As governments expanded and grew their bureaucracies – and especially when the United States began to tighten its immigration policies against what were then considered “undesirable” immigrants in southern and eastern Europe in the first half of the 20th century, then the whole idea of visas and quotas and restrictions based upon place of birth came into vogue.
And here we are now.