The other day I realized I could plug my ancient busted laptops' hard drives into my computer and dick around with XP again. 3d pinball was and remains the best game of all time
Although most software we develop now is designed to be upgraded or run on newer OSes. So there is less need to keep running old OSes.
But you can be certain that any new airport or trainstation will still run the same OSes as when they were build. Because it is better to encounter old problems you already know how to fix, than to encounter new problems. Especially if lives depend on it.