Part of what is great about playing a Paladin is walking into a village and having the people there trust you and your group, specifically because you are a Paladin.
It is a class that derives benefit from a well earned reputation for being exactly what it is.
I rather doubt that part of the inherent perks of playing a Paladin is meant to be people automatically trusting you. I understand that to a degree a Paladin is meant to be a respected member of the church, however most times they are meant to be the law bringers of an order. They are the martial arm of a religious order.
I should also like to point out that unless your campaign has some sort of adept type force always detecting good/evil, no one can tell whether a Paladin is who he says he is or not. Carrying a false holy symbol as a part of a disguise is easily done.
Also I would think that they would only get preferential treatment from those who prescribed to their beliefs and agreed with whatever the order was doing at the time.
There are a lot of different things to consider when you are talking about something like preferential treatment for Paladins.