The range is there because we are all different - some are smaller build than others. I recall years ago we were called ecto- endo- and meso- morphs (basically small, med and larger build).
Does anyone else remember this, before the advent of the BMI?
I am aiming to get into the lower healthy range of BMI because it will give me more flexibility. If I get to 25 and stay there, there isn't much leeway for gaining that inevitable half stone, as I expect will happen, you know?
I think the unhealthy (less than 18.5 and over 25) is what we should focus on avoiding - anywhere between those is all good!