The simple answer is that these office plans are cheaper. It's a common business pitfall. The cheaper short term solution wins in spite of long term health productivity and culture advantages.
That might be true in some cases but there's an entire industry built around renting open-plan workspaces to solo founders and freelancers who freely choose to spend an extra $5000 per year and an hour's commute time each day because they feel an "office environment" surrounded by other busy professionals focuses their mind better than the serene quiet of their bedside desk. Many of them are developers.
