I suspect most companies that absolutely need every inch of continuous desk space have bigger problems. Organic growth isn't difficult to manage, it's the crazy VC fueled hiring sprees that create real estate issues.
2. Physical security and confidentiality is much better.
3. If teams hold 'stand up meetings' or suchlike without using meeting rooms, they won't disrupt other teams.
4. People who have to make calls all the time (customer support, sales etc) don't disrupt other people.
5. Fixed walls remove the temptation to salami-slice square-footage-per-employee, protecting good working conditions.
6. Climate control becomes simpler and has a better chance of working.
Sound levels rise with the size of the crowd. More people making noise, more conversations more of the time, more space to spread the sound, and less individual accountability means people talk louder to be heard and are less considerate of their neighbors, creating a feedback cycle that ends up in a very rough environment.
I know that isn't the case for everybody, but I think I'd be quite comfortable in an 8 person war room as long as folks were actually working on stuff.
Plus, offices/cubes are not flexible at all -- when you start to outgrow your building full of offices (or even cubes), you can't easily squeeze desks together to make room while you seek additional space.
We have some small "phone rooms" that are about as small as you can build an office, and they are super cramped and uncomfortable, I wouldn't want to spend a full work-day in one.