BMI was introduced 200 years ago by Lambert Adolphe Jacques Quetelet. He was a mathematician, not a physician. He himself stated it should not be used to determine the level of fitness for an individual.
BMI is physiologically wrong. Bone is denser than muscle and twice as dense as fat; people with strong bones, good muscle tone and low fat will have a high BMI. Thus, even very fit people are obese according to it.
Insurance companies can charge higher premiums for people with a high BMI. A healthy person could live a long life paying high premiums.
We waste money treating healthy people who are"too fat". We allow doctors to use quackery instead of real medical practices. Eliminating BMI as a measure of health will encourage better diagnosis and improve body image for many Americans.