I would have agreed with you before I came to law school, but now I see why having intense legal training before being able to practice is required.
Being an attorney requires a very specific type of thinking which is somewhat different from normal human reasoning. It is less about understanding what is wrong or right morally, and more about knowing who or what sources have power, what laws and rules are relevant, and which levers should be pulled to argue for your desired outcome. It is this "thinking like a lawyer" that law school purports to teach, maybe even more so than the actual law itself.
Being an attorney is a huge responsibility, and I think the American Bar Association is right to set the bar high for prospective attorneys. My only gripe is that this bar seems to be not only ability and knowledge based, but also intensely financial as well.