The simple answer to WX man's question is - because they can. It's been taught that way for a long time and why the hell change. If you pilots Mil or civil cannot cope with QFE, QNH etc how the hell do you cope with mph, knots, or kmph, or feet, metres and flight levels, or lbs per min, galls per hour, or litres per week? In my day it was called airmanship and it was done mainly in the head. If you can't do it then stay on the ground where you belong.
I feel better now.... the Springbank helps.
