Spymaster has lost perspective on this one I think.
A bit like someone squashing on to the tube every morning, and thinking the tourists on the windy open top bus are somehow losers, simply because the tube is faster and indoors.
I'm of the opposite view. I know who is having a better time, and it's not me on the tube. (And, I suspect, Spymaster doesn't find his flights very much fun either. It's a chore he probably wishes he wasn't forced to do.)
For others though, sometimes, it's fun to travel. It's not all about speed or a conventional view of comfort. And indeed, there's little correlation with affluence either - in some cases quite the opposite. Someone, say, going to Australia overland is likely to be considerably wealthier - in terms of cash *and* time - than someone flying, even if they fly first class. Spymaster is probably time poor and cash constrained.
My favourite sleeper trip was to Berlin. We had a new compartment, with our own WC & shower. As we were coming into Berlin, the carriage conductor had laid out another empty compartment for us to use as a private breakfast space. He served us whilst we watched a snowy Berlin come into view. When we arrived we wheeled our bags 10 minutes to our apartment near the station in the city centre.
It wasn't cheap, but you couldn't get an experience like that flying unless you went by private jet.
The Caledonian sleeper isn't quite as plush of course, but it can still be fun for those who aren't living the tedium of frequent travel on that route.