The same goes for the number of complete idiots who seem to think you have to cross the start of the runway at 50ft as per commercial operations performance.
Who said anything about commercial operations.
It is well known by anyone flying commercially that commercial operations can often use the threshold height of 35ft (subject to certain requirements) and at other places the minimum threshold crossing height can be in excess of 50ft.
It is simply an industry standard that firstly the performance figures are based upon and that the safe clearance between the wheels and the obstacles under the flight path are based upon.
What a pity that no one has learned from the tragic fatal accident where two experienced pilots were killed and almost killed an innocent bystander under the approach throught hitting moving farm machinery in a field short of the threshold well below what would be considered the normal approach path.
It is imperative the instructors instill in students the simple basics i.e. that it is important to cross the threshold at a safe height and that since the performance figures are based on crossing the threshold at 50ft, then in the absence of any other safety issues that is a good figure to aim for.
Finally, the reason why most things are done in commercial operations is to ensure safety. So if doing X ensures safety and there is noting to gain from doing something different why unnecessarily endanger the flight?