https://news.yale.edu/2015/09/22/living-artifact-dutch-golde...
Here's a perfectly correct general statement: Any effort spent telling average people to not use BMI makes society less healthy. Average people are not getting BF% measured when you tell them not to use BMI. They are just ignoring all metrics and eating potato chips instead.
Spend less than you make is another one - sure there are edge cases where that is not appropriate. But in most cases, it is, but most people arguing that it doesn’t apply to them are they very people to whom it should apply most strongly.
I do agree with your general statement about its use.
There's no reason NOT to use it, generally, just recognize that it has severe limitations when applied to the individual. Notably, effects of training and exercise on health using BMI as any sort of baseline or incremental figure of merit.
Yes, it absolutely _does_ change. One might as well go all the way and start offering Oxygen or Water bonds. The immorality masking as morality here is insulting--not related, mortgage-backed CDOs during the financial crisis and "Pay Day" loans.
There are many, many fundamental individual needs and items (economic "utility") that, while financialization of them makes sense at the large scale (flood insurance, natural commodities trading, municipal infrastructure), makes zero sense (and is even amoral) on the individual and small scales.
Put another way, many bulk-health statistics (BMI, Blood Lipids, Heart-Rate) are useful to track for populations, but make little sense (and is wrong-headed) to extrapolate-down to the individual.
Just because you can, doesn't mean you should.