Not only are they most often right, but doctors know to under promise and over deliver. Which is better: "You'll never have use of that leg again" followed by a success story due to hard work and PT, or "Don't worry brah, that'll be healed in like two weeks" followed by a long slog of missed goals, unmet promises, and malpractice lawsuits? "You said I'd be walking in two weeks, and it's been two months!" Enjoy your new lawsuit!