I tend to ride distance events these days (Audax) - my road bike (1994 Litespeed Catalyst) is great for these being supremely comfortable.
I suspect that much of the current fashion for stiff bikes comes from historic marketing hype associated with the switch to Aluminium (which was more profitable for bike makers) - what you gain in power transfer you lose in fatigue, even assuming that the power transfer is real (some evidence suggests energy return and the frame acts only as a spring, giving a burst later in the pedal stroke).
Even though it has 1994-6 Record and Chorus bits on it, I still enjoy riding it all winter, so I guess it's still being used for its original purpose. I have never raced or TT'd even a kilometre.
In the winter I ride a lot at night, and for that I have a drop bar tourer built from a 1990 Marin Palisades frame, so that is definitely not used as originally intended!