They have. BIM is usually talked about in the same breath as waist circumference which would be a better measure of abdominal fat.

I

Same for me, no one considers BMI to be a good indicator of anything, but it is better than nothing, and more importantly, it is super simple.

Any idiot with a bathroom scale and a measuring tape can do it. And by adulthood, height doesn't change significantly and you probably know it, so you may not even need that measuring tape. Other metrics need specialized equipment, error prone or complex procedures, etc... I don't even know how to make a waist measurement. Where exactly? How relaxed should the subject be? How long after eating?...

That's the value of BMI: simple repeatable. Not the best but enough to get and idea and make statistics.