Flat structures work great for smaller organizations, but don't scale up with size.
That said, a bigger organization could still be structured like a federation of relatively independent businesses/departments, with clearly defined interactions (interfaces) between them, rather than a monolith.
Modular design benefits business as much as it does software architecture.
Perhaps better would be if I said "authoritarian" rather than "hierarchical". I don't think democracy requires lack of hierarchy. Or take the development of Linux kernel - although hierarchical, everybody has the same power.
And it can scale quite well. Switzerland and Mondragon are good examples.
That said, a bigger organization could still be structured like a federation of relatively independent businesses/departments, with clearly defined interactions (interfaces) between them, rather than a monolith.
Modular design benefits business as much as it does software architecture.