Blame deregulation; blame Freddy Laker. I’m old enough to remember when airline travel was so expensive, it made sense to travel by Greyhound bus, even if it took 48 hours to cross the country. I’m also old enough to remember DC4’s, and sucking on an oxygen tube in a DC3 flying to Cusco. My father made frequent trips overseas and frequently took Icelandic (which flew to Luxembourg, IIRC) because it was not part of the overpriced cartel monopolizing the transatlantic routes. Then Freddy Laker started an airline that refused to be part of the price collusion and the cost of European travel to and from North America plummeted as the other airlines eventually followed suit. IIRC, it was Jimmy Carter who pushed deregulation of the airlines domestically, forcing them to actually compete on price (but not, as we see today, on customer service).
Essentially, the cost of travel has plummeted, particularly the bargain basement travel in coach for those who don’t definitely have to be at their destination at certain time and have less demanding itinerarieis, r are willing to put up with less flexibility in travel to save money.
You can Google the statistics (which I can’t be bothered) but certainly airline travel increases every year for the last few decades. I assume the fall of the Iron Curtain and the reduction in unrest and bureaucracy worldwide has also made it easier for tourists to go where they want. (FYI as an example: I have been to Europe - Italy, Britain, France, Holland, Germany, Austria, Hungary, Spain; Australia and NZ twice; China, including Hong Kong and Tibet; Egypt, Turkey, Jordan, Israel and Palestine, Dubai, and India; we have another trip to Africa planned in a few months… and we’re not done yet. As a joke, when my wife’s cousin said “Where have you been?” she said - “where haven’t we been? Name somewhere.” So cousin picked randomly “Kazakhstan” and we could say “flew over it…”)
However, that’s only if you are part of the right people, born in the right country. As the US fight over immigration and visitor visas demonstrates, people from the wrong countries face a mighty uphill battle to even get to visit places like the USA and Canada. Our guide in Aswan mentioned that he’d helped an American family he was guiding when they had to take shelter during Arab Spring demonstrations, even hiding in his home because it was risky to drive through unpoliced crowds to their hotel; they invited him to visit them in the USA sometime. Unfortunately, he would never qualify for a visa. The USA looks for a steady job he would return to, a bank account, a family he would return to, assets enough to show he wasn’t planning to stay and work illegally in America, relatives who would vouch for him, etc. - everything that a recent unmarried college grad with an on-demand job simply did not have. There may be plenty of third world people who would be able to afford a once-in-a-lifetime dream trip to New York or London, but those countries won’t take a chance and let them in.
I should also point out there’s another insidious impediment to global travel. The current administration’s hostility to certain people is taking its toll. News reports that a teacher on a field trip from Canada to the USA was denied entry based on nothing more than his Muslim name prompted many Canadian schools and organizations (Girl guides) to cancel trips to the USA. (IIRC the same happened to a British teacher on a school trip). A recent article suggested that the number of foreign student applications in the USA is declining too.
So while travel for westerners may be easy and cheap in “best exotic Marigold” style, the doors are slamming shut for the third world inhabitants.