It is a fallacy however to assume that because someone is telling you something and getting paid to do so, that the being paid part is the only reason they are doing it. If you already believed that a car is the most valuable asset a person in America is likely to need, you would be more likely to become a car salesman than someone who is fundamentally opposed to the idea of cars. So the set of car salesmen is probably skewed toward the people who really believe in cars and would be preaching car stuff even if they weren’t paid to do it. But if you are passionate about something, and can get paid to do it, why would you not take it as your job, since it makes you more effective at doing the thing and also lets you do it full time.