The reason why many people distrust car salesmen is that we think car salesmen know something about the quality of a car that they are not telling us. They have incentives to lie: a good car without problems fetches a higher price than a lemon. Surely, a car salesman would like us to simply trust him that the car is a peach. Yet, even if we don’t believe that the salesman is honest, we may still decide to purchase the car. This is because there are mechanisms that help us manage our distrust, such as CarFax reports, warranties, and online feedback.
These mechanisms work reasonably well because the quality of cars is observable. Ultimately, we are going to find out whether a car is a peach or a lemon. This allows us to price warranties and create records of historical performance. It also helps individual car dealers to build up reputations for honesty even if we don’t trust car salesmen more generally. The market for cars does not collapse because we think that car dealers are dishonest.
In the case of religion, the problem is the “inscrutable nature of the good,” as the sociologist Diego Gambetta puts it. Clergymen have no private information about quality. Consumers cannot at reasonable expense discover the quality of promises, such as rewards in an afterlife. This means that the authority of clergy is intrinsically linked to how much we trust them. This is especially problematic for religions like Catholicism that rely strongly on the authoritativeness of clergy. That is why clergy in these religions invest so heavily in symbols that are difficult to imitate, such as celibacy. Celibacy tends to deter imposters. It is also why the Catholic Church is rightly worried about the consequences of declining trust.
Politicians occupy a difficult middle ground. Most of us would prefer an honest politician to a dishonest one. We have some institutions available to check dishonest politicians, such as elections and impeachment procedures, but they are highly imperfect. The quality of politicians is largely, though not fully, inscrutable. The outcomes politicians try to influence, such as health and economic well-being, are only shaped to a small degree by the policies politicians pursue (and each individual politician is only a little bit responsible for those policies). Why would you try hard and be an honest politician when you can be voted out of office for shark attacks or bad weather? Moreover, we care not just about the quality of the output politicians produce or their honesty but also their ideological leanings, ability to communicate, attractiveness and so on. The more of these factors matter, the more difficult it becomes to select out dishonest politicians.
Any political system would work better if politicians were honest. Unlike clergy, congressmen have few incentives to improve their overall reputation even if regard for Congress is at historic lows among the American public, although each individual congressman still has incentives to claim that he is more honest than his competitors. At least in this sense, politicians do look like car salesmen.