Yes - I am well aware of how the scam works. Plenty of other trades do cert 4 includng my own . I have personally had to remove 2 "licenced" plumbers from my property for substandard work - complete numpties
At school it was common threat of the teachers - "dont do the work and you will end up being a plumber" Some plumber looked at how the sparkies scammed the system and decided to follow suit ' I dont blame them - its a great job protection and wealth protection scam.
Most people dont realise that you can legally do the work your self - just needs to be done to the regs and signed off by the scammers