Unfortunately (or fortunately) I have come across instructors who just love hopeless students.
I know of three people who took over 100hrs. Two of them never got the PPL and
AFAIK (lost touch with them) continued to fly with an instructor in the RHS, and the third got her PPL after spending about £20,000. The instructor was telling me with glee how much she had spent. He had a special revenue maximisation technique which was to knock the student's confidence (easier to do with women, in general, perhaps?) just about the time he/she was making progress. In fact she got her PPL only after moving.
This instructor is not instructing anymore, TMK. But these practices were pretty widespread in one or two places I used to hang out.
Let's be brutally frank and cynical. The way the PPL training business is set up, the
business incentive to deliver a licensed (I should say "competent" but that would sound too ambitious) pilot is exactly zero. This isn't the RAF. There is therefore bound to be a (small) number of instructors who reach the obvious conclusion and have no problem with the ethics.