Because they don't have to. There is no legal requirement of them telling you the truth, in fact, when you sign a purchase contract, you literally sign a piece

Because they don't have to. There is no legal requirement of them telling you the truth, in fact, when you sign a purchase contract, you literally sign a piece of paper that states you cannot derive any rights to what the salesperson told you. Their job is not to inform you. Their job is to sell cars.