Having individual offices is is a lot more complex then just more space. Actually building these things is non trivial. It's not just walls, it's air con vents

Having individual offices is is a lot more complex then just more space. Actually building these things is non trivial. It's not just walls, it's air con vents, electrics, etc. I also think you may be underestimating the extra space required to make an office not feel like a closet. Then there is natural light. In a big open plan space light travels to the entire space. With offices you either need to build on the edge of the building and have a window, or make at least one wall out of glass (expensive). Even doing that you still can't just take a big room and turn it into partitioned offices. The capital outlay for a company to fit out a space with individual offices is actually really high and it all comes in one big hit. I'm sure if it was a matter of just paying 5k per employee extra per year the story would be different, but that isn't really a reality.