Informal hierarchies form in groups of friends, but as you say when it becomes a problem people can simply part ways. This isn't a good way to structure govern

Informal hierarchies form in groups of friends, but as you say when it becomes a problem people can simply part ways. This isn't a good way to structure governments or workplaces though, because simply walking away from your home or livelihood isn't as easy as finding new friends. That's why it's important for these things to have formal officially recognized hierarchies, with rules governing and regulating those hierarchies defining and limiting the ways they can behave.