My understanding is this is precisely backwards: using BMI to gauge your own health is inaccurate, but using it to analyze populations is the intended purpose.
As the country gets more fit, and that fat turns into muscle, what happens to the BMI? It either gets higher or stays the same, right? Certainly a good measure to perpetuate a crisis.
In the meantime, I more regularly see the people whose BMI is highly correlated with their body fat percentage; and, one of those requires a scale and a number that doesn't change after your early 20s. The other one requires a tape measure, calipers or an immersion pool.