I've scoured this thread and the only real reason I've seen the OP come up with as an excuse as to not install ring circuits is that they don't like testing and certifying them/can't be bothered with fixing existing mistakes? (If you're fixing mistakes, not only are you making installations safer for your customers, in business terms it's also more money to be made... just saying)
I'm only a trainee so I'm not gonna pretend I'm any sort of expert in regards to regulations and methods of installation for power circuits - because I'm not. But I can test a ring final just fine, surely if they're a qualified professional I'm sure they do it with relative ease?