When I bought mine, MF equipment was expensive and rare. 120 film was not always easily available, and when I found out I was going on a two-week trip to Africa I bought a 35mm back reasoning that it should always be possible to find 35mm film, and that was better than no film at all.
It turned out I was wrong - 120 film was easier to find (and get developed) in Cairo than at home - and there was no film of any type to be had in Eritrea.
But by then I had started to like the 135W back for the aspect ratio, so my next Bronica buy was a 40mm wide angle lens for great panos