|Katniss on her way to the Capitol.
Locomotives, or trains, first appeared in the middle of the 19th century, but they didn't really begin to incorporate high-end luxe amenities for first-class passengers until railway travel became more widespread in general, at the end of the 19th century. The opulence of long-distance trains, such as The Orient Express, is legendary: servants, fine china and crystal, sterling silver, elaborate meals, and plush carriages for those wealthy, often upper-class, passengers who could afford a first-class ticket. And for the rest? Trains, like ocean liners, are large enough to make the gulf between first-class and third-class passengers impossible to cross. Although it's not easy to use an airplane bathroom in first-class if you're traveling in economy class, one still shuffles through the first- and business-class (and economy "plus") seats on the way to those awful seats in the last row that don't recline, and the crafty economy air traveler can swipe a pillow or a blanket from an unused seat.
As a mass transportation technology, trains are better able to convey vast differences in passenger status than airplanes (or any flying transport). Their length makes it possible to have different entrances, different amenities, and different experiences for passengers, according to the cost of the ticket. And they hark back to the Gilded Age of the late-19th and early-20th centuries, when the gulf between the haves and the have-nots was similar to what it is now. No wonder that the creators of genre books and films have turned to them to realize a vision of a dystopic society that looks a lot like later-capitalist modernity. And no wonder that they're thriving today.