Because it wasn't designed by a physician? Because it shows me to barely be "normal" at 185, a weight I have never been since I reached this height. It ignores an entire range of factors, factors that could fairly easily be measured and included. Because across 40 studies surveying 250,000 people it showed that people with a BMI of 30-35 were at less risk of heart disease than those with a BMI of 20.
It's crap. It has been used for two centuries with no adjustments to make it fit better, how many medical procedures or tests have you seen that have not changed in 200 years? It's obsolete, and was created that way.
Jesus man. Its for a QUICK ESTIMATION. Do you really think your entire health profile can be broken down into two numbers?