A look at pro and anti articles in the New England Journal of Medicine seems to indicate no justification for the practice:

The annual medical is a kind of ceremonial or ritual which, according to its critics, is without rational foundation despite the fact that so many patients, and perhaps a majority of doctors, believe in it. This proves that superstition is not dead: but perhaps that is no fatal criticism of the annual medical after all, because superstition will never be dead. If it does not attach to one thing, it will attach to another.