Of the 1000 or so NPPLs, 50% are microlight pilots who can instruct on the NPPL albeit with an "exemption" rather than an instructor rating, becuse the powers that be screwed up the ANO amendment.
Of the 500 or so SEP NPPLs 95% are there because they can't get a Class 2 medical; a number of them are already experienced instructors! The question is, should they be allowed to instruct ab-initio students without an appropriate medical certificate?
We are now left with a handfull of ab-initio NPPL holders who supposedly took the cheap option,! The cost of gaining the relevant experience plus a FI course is the same regardless of licence type. The "enormous" financial saving by not having to pass the CPL written exams, would amount to less than 5% of the total cost.