Lets say I'm going to buy a Lamborghini from a guy named Steve. Now, Steve can tell me as much as he wants about how well it runs, and how nice it looks, but he can't tell my anything about the actual specifications of the car. Would you prefer to buy a car from someone who actually knows this information, or just some random dude who doesn't know anything about his own car? Even if the car runs like a beauty, I'd rather buy the car from someone who is a Lamborghini expert than someone who is not.