I seem to recall that the NPPL take up was mainly due to medicals - either that someone could no longer get a class 3 or couldn't get a class 2.
In my experience people are not saving much on the hours as they end up doing pretty much the same as everone doing the straight PPL anyway.
The one big advantage is that the NPPL training can be done from airfields that would normally not be approved for ab initio PPL training - e.g, BGA approved sites, reducing the costs for operating there by not having to have fire cover. Of course there is the opportunity to upgrade to a PPL out of the NPPL relatively simply as long as one can get the Class 2.
Why we cannot have the class 3 back beats me - the FAA has thousands and thousands of pilots with class 3's and they can fly IR, instruct and do many other types of flying with only a class 3 safely!