OK Let me clarify
What if I said 1000 hours of circuit bashing and still can't land. The number is not the important point, the point is that flying is definitely not for everybody. There are some (not many) who have very poor coordination, concentration, eyesight, motor skills or just cannot make a decision WHATEVER it is there are people out there who cannot safely fly an aircraft solo.
I am simply saying that if we have an assumption that nobody gets washed out then are we being realistic ? On the subject of naff instructors have a look at the failure rates for FI courses, same rules apply, there are some people who should not be qualified instructors because they haven't put the time in to gain experience and have simply paid for the rating.