There's cost, and there's availability. You will literally have a very hard time finding offices-based real estate in the silicon valley for any reasonable size

There's cost, and there's availability. You will literally have a very hard time finding offices-based real estate in the silicon valley for any reasonable size organization. Landlords don't build it. Let's say offices take 150 sqft per employee, and open plans take 75 sqft per employee. At $8 per sqft, this is an additional $600 per employee. Money out is easy to measure. Productivity and disruption (as well as serendipity) is close to impossible to measure accurately.