Subservience in human psychology
I was having some thoughts on the same topic. Free-will is not possible to exist in every human. Humans are a typical mix of conscitious being and un-conscitious beings. Not everyone can succeed in being self-aware, self-knowledgeable, and all that. In terms of Maslov's theory 'pyramids of needs', not all can reach the highest level of 'self actualisation', that is, well risen above the basic animal needs of Food and Sex.
So, if statistically the population is largely not into the self-consciousness, they need be 'guided and Taught' (=dominated) by those who are. It is desired by the good 'self-consciousness' men that all the people be trained to work from their free-will right from the child hood, but then aspirations and realities differ. That makes human a typical subjects of dominance, domestication by their own species.
We might already be having a scientifically studied explanation for servitude in humans in subjects of Psychology. This evolutionary aspect might have contributed in the social evolution of humans.
If Saudi Arabia has the Sharia laws to arrange deliver the subjugation effects on the larger population, the evolved British Democracy has found a democratic incarnation of such laws in the form of 'Anti-social Behavior laws' which are applied at certain crowded places to teach the visitors and 'citizenry' to conduct themselves rightly in order to avoid punishment. A kind of 'moral policing' is actively conducted in such places which are notified by law to be venue for these laws. The human actions which have been scientifically studied to be Anti-social are well described, such as Kissing, PDA, playing music in loud volume, smoking, drinking, talking or laughing in high voice, etc, and displayed for common knowledge, and later punished.
NPD is also likely to be sowed in the old animal instincts of humans. It will not be easy to make progress well, as a society, if we do not keep all members arrest with the minimal earnings the society has already achieved. Each newborn child might just revert back to animal days if not provided the 'good' education, you know.