According to aviation press reports I've seen (so they must be right...) 2/3 of NPPL candidates are existing PPL holders who no longer pass their CAA Class 2 medical.
Clearly this is not what anyone intended the NPPL to be.
The training industry (which is the most powerful GA lobby) wanted a PPL which looks cheaper on their price list.
But not all thought it would work. At the time, every instructor or flying school owner I spoke to told me the NPPL won't actually work out any cheaper because the pilot has still got to reach a standard where they can fly safely in UK's airspace. But the minimum NPPL requirement does look cheaper on the price list than the minimum PPL requirement!
Personally I think a complete revamp, with extensive modernisation, is called for but it will never happen. Certainly not before GA has shrunk to the insignificant levels seen in the outer reaches of Europe.