BMI isn't perfect by any stretch of the imagination. For example, I'm 5'5'' and weigh 160lbs. Currently trying to get down to 135lbs (which is less than my peak physical form in high school) and people balk at the idea that I can lose that much weight based on my appearance. Funnily, 115lbs is still considered healthy for someone my height. At the end of the day, it is much cheaper to read a scale and a measuring stick than use an expensive DEXA scan to get an accurate measure of body fat percentage.