Well the reason that a hierarchy exists is because people can be greedy, not because one person is better than another. Those who gain power rarely question the morals or ethics or reasons behind their power, because if they had a better understanding of the circumstances or reasons, they may not be able to conscientiously use that power.

If a king appointed you into some high position, you now have an advantage over most of the people in the town. If you question the ethics behind it, such as saying "Why do I have power over all these people, when I was once in that very group" then it goes hand in hand that you'd have qualms about using your power to your fullest benefit.

Compare that with religion. I'm not suggesting that it's exactly the same and that religious people have power over those who don't, but it's an interesting idea nonetheless. Someone of faith may believe they have an inherent advantage over a non believer (something like, I don't know, going to heaven).

Let's say that someone believes that it's very likely, by the way they're living, that they're going to heaven, why would they question the rules and ethics that get them there? It wouldn't make sense because they might lose their faith, or they might not like the result they find. realizing an unfairness.

A thought such as
Why would a person go to heaven and another go to hell, living identical lives, except one is a believer and the other isn't?
might come up. I personally think that it's unfair, and there's no good reason for it. In my mind, any truly just God would not care about such a trivial piece of information, especially one that is so hidden from people in the first place. I'd need a reason to believe why someone who believes is apparently better than someone who doesn't. If that reason is hidden, or simply not told, it's probably for an unjust reason.

So who would want to go from a mindset of being blessed with eternal life, to just another Joe that's going to be in the ground 100 years from now like everyone else? Not many, I'd bet.