“There are few people who get to decide what will happen in our world. You have been invited to join them. Pull back the curtain and take your seat.” This is what Cooper tells Don that finally leads him to buy a Cadillac. Don's realizing the American Dream, and buys his Cadillac to show that he's a baller. That's why you buy a Cadillac—to show off. And when you can do that, you drink, because no one can tell you what to do anymore. Oh, and then you litter.