Hierarchy relies upon obligatory allegiance
Power is the ability to win a conflict.
If the winner of a conflict is predetermined in advance - then there is an asymmetry of power.
The ability to win a conflict is determined by who takes your side.
In order to have stable asymmetries of power - you need permanent alliances which reliably win in any given conflict.
If the individual is free to choose which side they want to take in a conflict - or whether to take a side at all - then individuals can switch sides at any time.
If individuals are free to switch sides at any time - then permanent alliances cannot exist.
Therefore - some mechanism of obligatory and binding allegiance is required to hold coalitions together.
Without obligatory allegiance - coalitions are highly vulnerable to defection - and cannot reliably enforce hierarchy at all.