The traditional SE model is to pose questions about real-world problems and attract practical answers from experts. But what is a "real-world problem" on, say, SciFi varies from what one on, say, Network Engineering would be.
There are people, myself included, for whom travel itself is an interest, beyond just the destination. I may choose a particular mode of transportation or a particular route or a particular carrier to experience something new, or try to imagine something I've read about. As such, learning about the travel experience in a historical perspective can be informative and enriching even if it does not have a direct present-day application.
But that said, I do not want this site to lose focus. It could devolve into a "fanning" or "spotting" site full of obscure questions of the narrowest of interests (we have already pushed some operational and historical airline questions on Aviation.SE, but there is no equivalent for other modes). It could devolve into daydreaming about some or other supposed "golden age" someone just read about in a column, and the myths about flying clippers or ocean liners or private Pullmans or zeppelins. It could devolve into discussions about political history, international relations, war and conflict, and trade. At a point, we become a site about "fun facts" and obscure trivia, where the questions asked are only of interest to the person who asked, what we used to term "too localized" in the old closure system.
Of the example questions, only #2 seems a slam-dunk to me in terms of topicality, as a good answer will explain the origins of the passport as an internationally recognized document, providing background that helps enrich the travel experience. Question #1 or #5 might be answered well by describing how the service might have changed over time due to economic or political constraints or changing travel patterns. Questions #3 and #4 I would consider useless trivia, in the absence of other context, and vote to close.
Added: I have in the past answered various questions that might be of interest to travelers at some level on History.SE. I think they all still belong there, even though I no longer participate on that Stack, and would have flagged them for migration had they been asked here: