I admire your skill in teaching people that, I haven't a clue how I judge how high I am, I just sort of do it correctly through the grace of God I think. It works, if it ain't broke don't fix it.
There are degrees of precision in most every en devour in our lives,flying is only one example.
For sure we can fly with rather wide margins of precision and not wreck airplanes....however if it is not all that difficult to be very precise in our ability to judge closing distance to the landing area and be very precise in judging the height of the wheels from the runway then why not strive for that level of proficiency?
A good example of the ability to accurately judge height would be a skill that is mandatory for aerial applicators when applying chemicals that require an accuracy of one or two feet from the start to the finish of the application run.
How long do you think an Ag. pilot would last if thy could not judge height very accurately?