The terrible fuel consumption is only acceptable now because of the differentials introduced by taxation.
Looking at yachting - where the use of 'red diesel' is now subject to a 60/40 regime of taxation - and the EU are about to instigate action against the UK as it does not think this is acceptable (they want 100% taxation as in much of the rest of the EU). One political decision and the whole thing is over.
So we have turbine engines - which could probably be a bit cheaper to build, but which guzzle fuel - which is ok so long as it is not really taxed.
And for what is it worth the only small turbine I've experience of was on a microlight at Sun 'n Fun and it made as much noise as a full size jet aircraft!
I had always lusted after a turbine Maule - until the day I met a man who had one. With full tanks it is a single seater, with 4 people (FAA types) it has about 100 odd minutes endurance......