Ever since the 35mm small frame gained popularity in the mid-1900s it's well known (and perhaps lamented) the particular crop factor became a de-facto standard by late 1900s when people discussed their fields of view, a useful thing when talking about compositions, compression and other related things.
Nowadays one can say he's got a "35mm lens" when he means he bought a micro-4/3 lens with a focal length of 17mm. Perhaps not technically correct but as a "standard" the 35mm equivalency gets the point home. You know what kind of a field of view a 35mm lens sports.
How were these coffee machine conversations back then, before 35mm took over the world?
Was it just like "well I have this here lens says 200 mm on the side and it makes a mighty good portrait" and that be the end of that? :)