The open workroom was a relatively short fad pioneered by Frank Lloyd Wright. If you look at office buildings before that, they're much more similar to houses and apartments. Lots of rooms connected by hallways, staircases, and atriums. You can imagine the difficulty and expense of lighting a large open space without electricity.

In Europe I see a lot of companies with open space workrooms with some cubicles, maybe 30-40% of workers at those companies seem to work in them.

No, it wasn't. Most companies had separate offices, individual or with 2-4 desks in them.