It's hard to conceive of anyone meaningfully "harmed" by being a BMI outlier.
The only real occassion it comes up is when some lean and uncommonly athletic person gets miscategorized as obese and get warned of increased risks to their wellness if they don't lose weight. A warning which they generally laugh at because they know their own situation.
That's hardly "harm" -- "mild social nuisance" is more apt.
The harm is that are more likely to get prescribed unnecessary medications. Most people are not confident enough or not knowledgeable enough to wave off what doctors say.
Potentially for health insurance but I get the actuarial argument, especially since higher than typical weight regardless of fat composition puts higher than typical strain on your cardiovascular (and other) systems
That is doubtful, but possible
It is used for individuals. That is where it is harmful