Where did you get this idea from?
At best, companies have team rooms that hosts 5-8 people but not individual offices.
Most of the time we all have our doors wide open, it's glass doors, mostly glass walls, very bright, very modern. Everybody is welcome to stop by at any time when the door is open. Door closed means "please don't disturb unless it's an emergency". People close doors to have longer discussions, to have confidential discussions, or to have peace and quiet.
The doors basically serve the same purpose as headsets. They just make more sense and are more ... human.
Yes, some offices house more than one person. Typically 2, some have 3. But the employees in this situation are quite content with this and could request single offices at any time.
Site managers in North America rarely want to hear this, since it's more expensive and supposedly prevents close collaboration and encourages slackers, but that's just a bunch of BS. It's absolutely fantastic to just be able to close your door and have peace and quiet if you need to get into flow. Much better than being forced to wear headphones all day, for noise-cancellation or forced-music-listening instead.