And why would the CAA/JAA have an instructor rating for PPL holders?
PPL flying was traditionally a recreational activity that generally takes place within clubs. Like many other recreational activities, you will find instructors who do it for enjoyment, to pass on their experience and expertise. The BGA has retained its recreational status throughout.
I thought the first principal of "prostitution" was that it involves money changing hands; it is after all the oldest profession. Instructors who work for free surely do not qualify for such a title, they are just enthusiastic amateurs.
If an instructor does not need to earn money then the best of luck to them in this rip off World.