"I am at a loss to understand why there is such resistance to installing them"
Most of UK GA is just managing, scraping out the bottom of the barrel, that's why.
It's also probably not worth doing on a carb engine. You pay less for the plane but you then pay for ever by having to pour extra fuel into it. Same with fixed landing gear; lower purchase price and extra 20% or so on the juice, for ever after.
If you could buy an EDM700, mail order from the USA, and install it yourself, you would get the job done for about half the price.