further to Frank & Hillaries post I would dare to add that a large factor involved with the choice of equipment was the stock of the cyclist's local supplier.
Use of the LBS was still the norm. many shops only supplied from certain whole salers.
so if your local shop bought from Ron Kit, you rode TA, Huret, Zeus or Suntour when it came along. Joe Whisker was the wholesaler with Campag (best prices) and RSI (Evian) the Stronglight and Simplex suppliers.
These were obviously not hard and fast rules, but it certainly made a difference
Martin Coopland, Scotland, BatesBicycles.com