That’s an easy one. Because rail is romantic; buses are not. It’s the same reason why we have movies called “Strangers on a Train” and “Polar Express” instead of “Strangers on a Bus” and “Polar Greyhound.”
Trains, be they steam locomotives or modern commuter rail, have a certain romantic appeal, even a sense of glamor and luxury. Think of all the films, TV shows, and novels in which rail travel plays a central role. Now think of the few films, TV shows, and novels in which bus travel plays a central role.
In most cases rail travel is entirely irrational. Yet people still advocate spending huge sums on it — even when it can be proven to be a money pit — because they just like trains.
I think the general perception of trains vs. buses can be summed up with the following images:
