Take Jimi Hendrix waiting acoustically on the platform here, determined to make it big. And he's not alone in singing on the station platform. Jimi's leaving home, but when Paul Simon wrote his tune he was Homeward Bound, and these folk from Belgrade are making a return visit back home on a Sentimental Journey (stick with it, some lovely performances there).
Perhaps that's part of the answer: the emotional journey. For the songwriter scratching for a theme, the train is a natural choice: a big journey that marks a transition in life, an emotional peg on which the song can be hung. In fact as Paul Simon explains in Train in the Distance, it's all about the hope that comes with a journey, real or imagined: "The thought that life could be better is woven indelibly into our hearts and our brains". (Aside - there is no-one quite like Paul Simon for writing literate lyrics that look like prose but still work as song).
Then, for some train songs it's all about the rhythm: Choo choo ch'boogie - "I love to hear the rhythm of the clicketty clack". How about Chattanooga Choo choo, not to mention the shuffling madness of Locomotive Breath, or the skiffling Rock Island Line?
Hmm, did I hear a train whistle in that? It's not the only song to want to emulate that evocative sound. I'd include in my count, Night Train, Take the A Train, and many more.
But of all these train songs, for my money, there is none more moving or expressive than Hugh Masekela's Stimela. It has it all: the emotional journey, the rhythm, and a very fine train whistle.