I don't think there was ever a time where every office worker had their own office. Only the big boss got their own office and everyone else had desks in a large room. The open floor plan we have now is pretty typical of what they used to look like.

Here's a good example:

https://www.officemuseum.com/1935_Auditor_of_Overcharge_Clai...

More pictures:

https://www.officemuseum.com/photo_gallery_1930s_1940s.htm

There are plenty of places where offices were the norm some years ago. When I worked in Germany the standard was either single Offices or team offices With max 5 people. In the US IBM also had offices when I contracted there. Microsoft always talked about their offices as important. Developers sitting elbow to elbow in a room with dozens of people is a fairly recent development from what I have seen. The need for headsets to get some quiet also seems fairly new.

That's interesting, but I'm unsure how much we can generalize from some photos. For example, I wonder how much "photogenic bias" [0] and survivorship bias exist in such photographic evidence. How many photographers of the time would take a picture of a hallway of private offices? And what editor would keep such photographs for posterity?

[0] There's probably a better term for this...

You're probably looking for "selection bias" in some sense, where the photos exist but they aren't being looked for so they aren't found.

THere are a bunch of places where 2 to 3 pps are in the office. I never accepted a job that didn't involve me having an office like that.

Office pictures from the Great Depression are not very convincing ;-)