Is it a bike you've had for years, and you ride it for sentimental value?
Is it a nostalgia thing?
Is it a fashion thing?
Do you just like the feel of the steel frame, or other parts?
I'm somewhat new to cycling, so I don't know. But around my city, I see guys who look like pretty serious cyclists, wearing some nice gear, riding old school.
I've got my eye on this Nishiki for my 2nd bike: