Coordination without any kind of hierarchy has N!/2 complexity. That gets overwhelming way to soon.
Have an idea that requires everyone else to change something. N!/2 conversations to have. (Or one big meeting with the same sort of complexity).
Need to change your approach to match what others are doing, gotta make a 1-on-1 connection. If they need to change their approach, they need to coordinate with others, continue for a long time.
If you want any kind of efficiency
You need to have small-ish teams. I'd guess about 10 people. But lets say 50. You need to chunk up work so that teams can work in parallel. You need central oversight to coordinate the teams. This can be just a group meeting of team leaders, but the big picture should not be lost. And you need to make some decisions from this central picture.
Isn't hierarchy standing in for encapsulation here? Companies interact with one another in a coordinated way with neither a hierarchy, nor needing to know what every other company is doing
If you want any kind of efficiency You need to have small-ish teams. I'd guess about 10 people. But lets say 50. You need to chunk up work so that teams can work in parallel. You need central oversight to coordinate the teams. This can be just a group meeting of team leaders, but the big picture should not be lost. And you need to make some decisions from this central picture.
All of this very quickly leads to hierarchy.