Happy new year to you all.
The current system is a shambles, with no thought being given to those whose only interest is recreational flying.
The take up of the NPPL by new students at clubs I'm familiar with has been non-existant, only people struggling for a medical seem to be interested.
Personally, I would be a bit miffed to have lesser mortals teaching at the same standard as myself!
If you want to teach a subject to any proper depth, then you need to have more knowledge than you are trying to put across. CPL teaches PPL, ATPL teaches CPL etc. etc.
Whilst parts of the CPL course aren't totally relevant to PPL instruction, so what? The more knowledge you have about all aspects of flying, the better instructor you tend to be.
In Helicopter instruction there are still a large number of PPL instructors since they were and still are able to be paid for teaching (very well compared to fixed wing FI's). Since the advent of the requirements for CPL qualified instructors and a minimum of 300hrs TT on heli's, the number of new instructors has fallen through the floor, it has simply become too expensive to bother.
Has the quality of instruction got better? It's still to early to tell properly, but I doubt it.