Why throw a piece of twiddly plastic at a problem whose input data is so inaccurate, and whose output data cannot be utilised to its apparent accuracy (never mind its actual accuracy), when doing "max drift is half the wind" in your head is almost instant, and (unlike fiddling with the slide rule) can be done in the air?
If the silly WW1 slide rule was removed from PPL training, the hours saved could be used to teach useful navigation.