Roll film cameras could be simple and inexpensive, and offer acceptable results from meniscus or triplet lenses. Amateurs didn't shoot a lot of film because it was expensive stuff reserved for special occasions. 35mm cameras demanded good optics, which were costly. Enthusiasts opted for upfront camera costs and cheaper film per shot.
Professional camera formats depended on how technically conservative picture editors were. Specialist picture publications which were popular in the pre and post WW2 decades, had no trouble with 35mm for print. Regional newspapers tended to be more conservative, with national press somewhere in between. Right up to the end of film, magazines insisted on roll film exclusively for publication, with no obvious aesthetic advantage to the format in print. This was for two reasons in my experience. First was resistance from picture editors to using a light box and lupe to look at slides. Many preferred to hold up a transparency to window light, only checking for focus through a lens after selection. The second reason was resistance in the print industry to small image sources, when making colour plates. Print technicians were dismissive of 35mm for illustration purposes.
A good guide to professional cameras at a given time, are motor shows. These were annual events with huge financial implications - most UK vehicles were homegrown, US likewise - which attracted press and newsreel photographers. Cinema newsreels emphasised the importance of the event by shooting Fleet Street photographers and their cameras, often photographing scantily clad ladies on cars, perpetuating the idea of photographers as louche and rakish individuals.
The Ideal Home exhibition, boat shows and similar annual events are good for camera spotting.