There really are people that will work on bikes for the joy of it, and not hatchet job every non-531 frame into a fixie...
I have built up a couple old Steel framed, 70's riders, into single speed/fixed gear bikes.
I don't ride too much single/fixed, but I will say this (at my age, 51) I don't see it as something that is that bad for your health (joints)
It forces the rider to be more AWARE of their surroundings... to be in control of the bike as your legs do most of the starting/stopping. I can see the attraction. Around town, over lever ground as a commuter, or to the cafe... what could be better than two wheels and a brake?
As far as hatcheting up old reynolds frames?
The bikes that I resurrected had spent the better part of 2 decades, collecting dust in garages and basements. They got new life and are in use again (one by my 20 year old daughter who just FLIPPED when she rode the fixie the first time). There are some purists out there who have the time (and $$) and inclination to piece together and re-build 70's 10-12 speeds up again. Things evolve. If a steel frame is revived into a spry around town rider... so be it. Better than being ignored. In ten years, that old bike hanging in the rafters might get torn down and recycled anyway.
*plink plink*